Meaning: To 'conduct' means to carry out or perform an activity, especially in a systematic way, such as an experiment.

Wrong options:

• figure: The word 'figure' is a noun that refers to a number or a shape, which does not fit the context of performing an experiment.
• collect: While 'collect' is a verb, it is not suitable here as it refers to gathering data rather than performing an experiment.
• collection: 'Collection' is a noun that refers to a group of items gathered together, which does not fit the grammatical structure needed for this blank.
• international: 'International' is an adjective that describes something involving multiple countries, which does not relate to the action of performing an experiment.
• natural: 'Natural' is an adjective that describes something existing in nature, which does not fit the action of conducting an experiment.
• social: 'Social' is an adjective that pertains to society or social relations, which is irrelevant in the context of conducting an experiment.

Correct answer: collect

Explanation: The verb 'collect' fits perfectly as it describes the action of gathering data, which is a crucial step in the research process. It maintains the parallel structure with 'conduct' and aligns with the subject 'researchers'.

Meaning: To 'collect' means to gather or accumulate information or data systematically.

Wrong options:

• figure: 'Figure' does not fit as it is a noun and does not describe the action of gathering data.
• conduct: While 'conduct' is a verb, it is already used in the previous blank and does not fit here as it refers to performing an experiment, not gathering data.
• collection: 'Collection' is a noun and does not fit grammatically as it does not describe an action.
• international: 'International' is an adjective and does not relate to the action of gathering data.
• natural: 'Natural' is an adjective that describes something existing in nature, which does not fit the action of collecting data.
• significant: 'Significant' is an adjective that describes importance, which does not relate to the action of gathering data.

Correct answer: international

Explanation: The adjective 'international' is appropriate as it describes the type of journal where researchers publish their work, indicating that it is recognized across multiple countries. It fits grammatically as it modifies the noun 'journal'.

Meaning: 'International' refers to something that involves or relates to multiple countries or nations.

Wrong options:

• figure: 'Figure' is a noun that does not describe a type of journal and is irrelevant in this context.
• collect: 'Collect' is a verb and does not fit as it does not describe a type of journal.
• collection: 'Collection' is a noun that refers to a group of items, which does not fit the context of describing a journal.
• natural: 'Natural' is an adjective that describes something existing in nature, which does not relate to the type of journal.
• significant: 'Significant' is an adjective that describes importance, which does not fit as it does not describe the type of journal.
• social: 'Social' is an adjective that pertains to society, which does not fit the context of a scientific journal.

Correct answer: significant

Explanation: The adjective 'significant' is suitable as it describes the extent of the increase in citizen scientists, indicating that it is noteworthy or important. It fits grammatically as it modifies the noun 'increase'.

Meaning: 'Significant' means important or noteworthy, especially in terms of impact or degree.

Wrong options:

• figure: 'Figure' is a noun that does not describe the extent of an increase and is irrelevant in this context.
• collect: 'Collect' is a verb and does not fit as it does not describe the nature of the increase.
• collection: 'Collection' is a noun that refers to a group of items, which does not fit the context of describing an increase.
• international: 'International' is an adjective that describes something involving multiple countries, which does not relate to the nature of the increase.
• natural: 'Natural' is an adjective that describes something existing in nature, which does not fit the context of describing an increase.
• social: 'Social' is an adjective that pertains to society, which does not fit the context of describing an increase.

Correct answer: natural

Explanation: The adjective 'natural' is appropriate as it describes the type of science that citizen scientists are engaging with, indicating that it pertains to the physical world. It fits grammatically as it modifies the noun 'science'.

Meaning: 'Natural' refers to something that exists in nature, particularly in the context of scientific disciplines like biology, chemistry, and physics.

Wrong options:

• figure: 'Figure' is a noun that does not describe a type of science and is irrelevant in this context.
• collect: 'Collect' is a verb and does not fit as it does not describe a type of science.
• collection: 'Collection' is a noun that refers to a group of items, which does not fit the context of describing a type of science.
• significant: 'Significant' is an adjective that describes importance, which does not fit as it does not describe a type of science.
• international: 'International' is an adjective that describes something involving multiple countries, which does not relate to the type of science.
• social: 'Social' is an adjective that pertains to society, which does not fit the context of describing a type of science.