Question

Choose the word or phrase that best completes the sentence.
A letterbox is a narrow opening in a door through ____ mail is delivered.
a. it
b. that
c. which
d. where

Answer 1

Hint: Identify the subject in the given sentence. Understand the meaning of the given sentence and use the method of elimination to arrive at the correct answer. The answer will be clear due to the subject.

Complete answer:
A pronoun is a word that is frequently used as a replacement/substitute for a noun when the sentence requires it. It is sometimes used because the noun cannot be repeatedly used.
There are various kinds of pronouns but the ones we specifically require for this question are called relative pronouns. These pronouns are used in the middle of sentences in order to contextualize the phrase that comes after.

Now that we know what these pronouns are, let’s look at our options one by one-
a. it - This is a pure pronoun that is used to replace a subject. This does not fit into the given sentence. This does not contextualize the given sentence any further. This is not the required answer. So, this is an incorrect option.
b. that - This is an adverb and not a pronoun. This does not fit into the given sentence. This does not contextualize the given sentence any further. This is not the required answer. So, this is an incorrect option.
c. which - This is a pronoun and it fits into the given sentence perfectly. This helps us to contextualize the given sentence. This is the required answer. So, this is the correct option.
d. where - This is a pronoun, which describes the location. This does not fit into the given sentence. This does not contextualize the given sentence any further. This is not the required answer. So, this is an incorrect option.

Note:
 The subject, verb, and object should all match with each other. The plurality of the verb should also align with the given subject.