Explanation:
> "I ____ to gain admission to the college for the past three years."

The phrase "for the past three years" shows that the action started in the past and is still continuing. In English, we use the present perfect continuous tense ("have been + verb-ing") for such situations.

Now, let's go through the options:

- A. have been trying — This is the correct present perfect continuous form, showing ongoing effort over time. Correct.
- B. tried — Simple past; it suggests a completed action, not something continuing up to now. Incorrect.
- C. am trying — Present continuous; suggests only a current action, not something ongoing over years. Incorrect.
- D. was trying — Past continuous; refers to a continuous action in the past but not necessarily continuing now. Incorrect.
- E. try — Simple present; does not match the time frame indicated by "for the past three years." Incorrect.