Meaning: 'Found' means to be located or discovered in a particular place.

Wrong options:

• depicted: 'Depicted' means to represent or show something, which does not fit the context of lakes being present in a location.
• forseen: 'Forseen' is a misspelling of 'foreseen,' which means predicted or anticipated, and does not apply to the physical presence of lakes.
• told: 'Told' means to inform or narrate, which is not relevant to the context of lakes being present in specific areas.

Correct answer: how

Explanation: 'How' is the appropriate choice as it introduces a question regarding the method or manner in which fish reach isolated lakes, aligning perfectly with the inquiry posed in the sentence.

Meaning: 'How' refers to the manner or way something happens.

Wrong options:

• why: 'Why' asks for a reason, which does not fit the context of asking about the method of fish reaching the lakes.
• whether: 'Whether' introduces alternatives or possibilities, which is not suitable for the question being asked.
• where: 'Where' inquires about a location, which does not address the method of fish reaching the lakes.

Correct answer: was already

Explanation: 'Was already' fits grammatically as it indicates a past action that has been completed, aligning with the context of the question being previously addressed by scientists.

Meaning: 'Was already' indicates that something occurred in the past before now.

Wrong options:

• has already: 'Has already' suggests a present perfect tense, which does not match the past context of the sentence.
• was been: 'Was been' is grammatically incorrect as it combines past and perfect tenses improperly.
• been: 'Been' alone is not a complete verb phrase and does not convey the necessary past action.

Correct answer: responsible

Explanation: 'Responsible' is the correct choice as it indicates that water birds are the agents or causes of fish dispersal, fitting logically and contextually within the sentence.

Meaning: 'Responsible' means being the cause of something or having a duty to take care of something.

Wrong options:

• despicable: 'Despicable' means deserving hatred or contempt, which does not fit the context of the sentence.
• distinguishable: 'Distinguishable' means able to be recognized as different, which does not relate to the role of birds in fish dispersal.
• vulnerable: 'Vulnerable' means susceptible to harm, which is not relevant to the context of the birds' role in dispersing fish.

Correct answer: stick

Explanation: 'Stick' is the correct answer as it describes the action of fish eggs adhering to the feathers or feet of water birds, fitting both grammatically and contextually in the sentence.

Meaning: 'Stick' means to adhere or attach to something.

Wrong options:

• add: 'Add' means to join or combine, which does not fit the context of fish eggs adhering to birds.
• rise: 'Rise' means to move upward, which does not relate to the action of fish eggs in this context.
• merge: 'Merge' means to combine or blend, which is not applicable to the action of fish eggs sticking to birds.