A verb tense question with two sentences tests how different forms of one verb show when something happens. Find the subject and check that the choices agree with it, then find the time clues across both sentences. Ask where a time span ends. The simple past names a finished past event; has or have links the past to now; had looks back from a later past moment; will looks ahead. A tense needs support from the passage, not only a form that sounds natural.
Hints
- Hint 1
Read both sentences for time clues, including the words before the ecologist’s name and the phrase after “populations.”
- Hint 2
Ask where the eight-year span ends. How do the time clues in the first sentence help you read that span?
Step-by-step
Follow the time clues
Step 1Check what changes
Start with Participants, the subject that tells us who keeps the logs. What changes across the choices? Each form fits that plural subject, but each puts the logging in a different time, so time, not number, decides. Because the participants belong to the program described in the first sentence, we should read both sentences for clues about when they keep their logs.
- Step 2
Find where the span ends
Where does the span in for the past eight years end? That phrase measures backward from now, so the logging covers a span reaching the present rather than a finished period long ago. The first sentence supports that reading: Since 2015 names the program’s starting point, while has directed links that past start to now. There’s no later past event that ends the span. The logging runs from the past up to now, within the same program.
- Step 3
Choose the tense
The present perfect is the tense that links a past span to now, using has or have and a verb form such as maintained. Had maintained needs a later past moment, maintained closes the span in the past, and will maintain places it in the future. With the plural subject Participants, the present perfect is have maintained, which shows the logging over the whole span up to now. Choice B.