Question 170·Medium·Form, Structure, and Sense
Since 2015, ecologist Maya Hernandez has directed a citizen-science program to monitor migratory birds. Participants ______ detailed logs of local bird populations for the past eight years, providing valuable data for conservation efforts.
Which choice completes the text so that it conforms to the conventions of Standard English?
For verb-tense questions, always underline time clues like "since," "for the past," "by 2020," or "next year." Decide whether the action is completed, ongoing from past to present, or in the future, and then pick the tense that matches that timeline. Finally, check that the helping verb (have/has/had/will) agrees with the subject in number (singular vs. plural) and fits the time frame indicated by the sentence.
Hints
Use the time expressions
Focus on the phrases "Since 2015" and "for the past eight years." Do these describe only the past, only the future, or something that started in the past and continues to now?
Connect meaning to tense
Ask yourself: Are the participants still keeping logs now, or did they stop in the past? Choose a tense that can show an ongoing situation from the past up through the present.
Check subject–verb agreement
The subject is "Participants" (plural). Make sure the verb form you choose correctly agrees with this plural subject.
Step-by-step Explanation
Understand the time frame
Look at the time clues in the sentence: "Since 2015" and "for the past eight years." Both of these phrases usually describe an action that began in the past and continues up to the present.
Match the time frame to the verb tense
When English describes an action that started in the past and is still true or ongoing now, it generally uses the present perfect tense, which has the form have/has + past participle (for example, "have worked," "has lived"). Because the subject here is plural ("Participants"), the correct helping verb would be have, not has.
Test each option against the time frame and grammar
Now check each answer:
- "had maintained" is past perfect, which describes something that happened before another past event, not up to the present.
- "maintained" is simple past, which usually suggests the action is finished.
- "will maintain" is future, which does not fit with "for the past eight years."
- Only "have maintained" is present perfect, agrees with the plural subject "Participants," and matches an action that has been continuing from 2015 up to now. So the correct choice is "have maintained."