Put the verb in the correct form:
We went to Kate’s house but she _______ at home. (be)
(a)isn’t
(b)hasn’t been
(c)wasn’t
(d)haven’t been

Hint: Look for pointers suggesting which tense to use. The action has already occurred in the given sentence. These pointers are indicators of certain tenses.

Complete answer: We can infer that the mentioned action has already happened in case of the reported speech.
This means that the sentence requires some form of past tense. Any form of the past tense
can technically fit into the blank, as all past tenses signify the action being completed. The tenses of present and future cannot fit into this sentence, as we need only the past tense.

The first part of the given sentence already tells us which tense to use, as the verb used is ‘went’. The word ‘went’ is the past tense of the verb ‘to go’.
Now, we know what we are looking for. Let’s look at the given options:
(a)isn’t - The word “isn’t” is in the present tense. This means that the action has been stated as a fact. This does not fit into the given sentence. This is not the required answer. So, this is an incorrect option.
(b)hasn’t been - The word “hasn’t” is in the present perfect tense. This means that the action is vague. This does not fit into the given sentence. This is not the required answer. So, this is an incorrect option.
(c)wasn’t - The word “wasn’t” is in the past tense. This means that the action has been completed. This fits perfectly into the given sentence. This is the required answer. So, this is the correct option.
(d)haven’t been - The word “haven’t” is in the present perfect tense. This means that the action is vague. This does not fit into the given sentence. This is not the required answer. So, this is an incorrect option.

Note: Choose the most appropriate option given the context of the sentence. Make sure all the forms of verbs are aligning with each other and work with each other perfectly.