Question

Fill in the blank with the most appropriate option.
We ____ our breakfast half an hour ago.
a) Finished
b) have finished
c) had finished
d) none of these

Answer 1

Hint: We know that verbs are action words and used to express an occurrence, action, or state. It is the grammatical center of the predicate in a sentence.

Complete answer:
From reading the sentence in the question, we can very clearly understand that the action being talked about in the sentence has already taken place, but the said action has not taken place a very long time back, but in fact, it has been completed just half an hour ago. Another grammatical rule that we need to remember for this question is that The past perfect is usually used to indicate the ‘past in the past’. In other words, when we refer to two past activities we may put the one occurring first in the past perfect as in “When I reached the railway station, the train had left”

Keeping in mind the above two points we can very easily understand that the form of the verb which we are supposed to use to fill in the blank should not be of perfect tense category.
Option ‘a’ is the correct answer because ‘finished’ is a verb in the simple past tense.
Option b is incorrect as it is the Present Perfect. An hour ago is in the past (a past time) and isn't connected to the present anyhow. If it were still happening it would be correct.
Option c is also not correct for the rules we have discussed above and since option ‘a’ is right, option d is incorrect.

Note:
Recalling the correct rules for a specific question is very important to reach the correct answer because grammatical questions you will get wrong if you resort to guesswork!