Question

Fill in the blank with the appropriate option
I met her at yesterday’s party, but I ______ her by sight for years before that.
a) Had known
b) Have known
c) Will have known
d) Had been known

Answer 1

Hint: To answer a question on tenses, always check the tense already used. "Met" is in the past tense so the answer should also be in the past tense. Now check the tenses given in the options and see which one is in the past tense. Then use it in the blank given in the question and check if the sentence is making sense.

Complete answer:
The correct option is option a. I met her at yesterday's party, but I had known her by sight years before that. This means that even before I met her at the party, I knew how she looks before I met her in person.
Option b is wrong because have known as present tense. Have known is wrong because when we use have known it sounds like there is something else to be added to the sentence. But the main event (meeting her at yesterday's party) has already been narrated.
Option c is wrong because it is in the future tense. In no way can the answer be in the future tense because the first part of the sentence is already in the past tense.
Option d is wrong because the use of "been" is incorrect.

Note:
  There is a chance of confusion between options a and b but always remember that the clue (the usage of the past tense "met" is the clue in the given sentence) is usually in the question itself. If you are confused with the use of tense in the given question, use the option in the given sentence. You may also use it in a sentence of your own. Make some other sentence with the option and relate it to the sentence given.