Question

Fill in the blank with the most appropriate word.
I would have called him right away if I _____ his telephone number.
a. have known
b. will know
c. had known
d. would know

Answer 1

Hint:Look for pointers suggesting which tense to use. The action has technically occurred in the given sentence, however, at a given time. These pointers are indicators of certain tenses.

Complete answer: Let us look at the given sentences first:
The first part states that the subject would have called him if the situation was different. This means that they are still counting on her to do something. So, it is an incomplete action, in the present tense.
The next part starts with ‘if’. This word is a conditional word. So, the tense used after
this, for this sentence, should be past perfect tense since the first part is already in the conditional tense.

This means that the tense that fits perfectly is the past perfect tense. The past perfect tense is usually formed by adding the helping verb ‘had’ to a past participle.
Now we know what we are looking for. Let’s look at the given options:
a. have known - This option is not in the past perfect tense, it is in the present perfect tense. This is not the tense that is required. This is not the required answer. So, this is an incorrect option.
b. will know - This option is not in the past perfect tense, it is in the simple future tense. This is not the tense that is required. This is not the required answer. So, this is an incorrect option.
c. had known - This option is in the past perfect tense. This is the tense that is required. This is the required answer. So, this is the correct option.
d. would know - This option is not in the past perfect tense, it is in the conditional tense. This is not the tense that is required. This is not the required answer. So, this is an incorrect option.
Therefore, option c. is correct.

Note: We often use the Past Perfect in reported speech after verbs like said, told, asked, thought, wondered etc.