Meaning: 'Resembles' means to look like or be similar to something else, indicating that the platypus's bill has a likeness to that of a waterfowl.

Wrong options:

• say: The verb 'say' does not convey similarity and is typically used for reporting speech, making it contextually inappropriate here.
• looks: While 'looks' could imply appearance, it is less formal and does not fit as well as 'resembles' in this context of comparison.
• likely: The word 'likely' suggests probability rather than similarity, which does not fit the grammatical structure needed in this sentence.

Correct answer: developed

Explanation: The word 'developed' is the correct choice as it is a past participle that indicates the advanced state of the sensory organ, fitting grammatically and contextually with the sentence structure. It aligns with the idea of having a unique ability that has been cultivated over time.

Meaning: 'Developed' means to have grown or advanced in complexity or capability, indicating that the platypus has a highly sophisticated sensory organ.

Wrong options:

• installed: The term 'installed' implies a physical placement or setup, which does not accurately describe the natural evolution of a sensory organ.
• pervasive: 'Pervasive' means widespread, which does not fit the context of describing the specific capability of the platypus's sensory organ.
• dependent: The word 'dependent' suggests reliance on something else, which does not convey the intended meaning of the organ's sophistication.

Correct answer: there

Explanation: The word 'there' is the correct choice as it serves as an introductory adverb indicating existence, fitting grammatically and contextually to introduce the subject of the webbed feet. It aligns with the structure of the sentence, which discusses the characteristics of the platypus.

Meaning: 'There' is used to indicate the presence of something, in this case, the webbed feet of the platypus.

Wrong options:

• so: The word 'so' is typically used to indicate a consequence or degree, which does not fit the context of introducing a new subject.
• as: The word 'as' is used for comparisons or to indicate a role, which does not appropriately introduce the existence of the webbed feet.
• their: The word 'their' is a possessive pronoun that does not fit grammatically in this context, as it would require a noun to follow.

Correct answer: hardly

Explanation: The word 'hardly' is the correct choice as it functions as an adverb indicating that the back feet are not used much at all, fitting grammatically and contextually within the sentence. It conveys the intended meaning of minimal usage effectively.

Meaning: 'Hardly' means barely or scarcely, indicating that the back feet of the platypus are not utilized significantly while swimming.

Wrong options:

• purportedly: The term 'purportedly' suggests something is claimed or alleged, which does not fit the context of describing actual usage.
• legged: The word 'legged' is an adjective that does not fit grammatically in this context, as it does not convey the intended meaning of usage.
• lagged: The word 'lagged' implies falling behind or being delayed, which does not accurately describe the usage of the back feet.