Question

Fill in the blank with the most appropriate word.
The population of Moscow has increased rapidly. As a result there is a housing shortage.
As a result of the population of Moscow _____ rapidly, there is a housing shortage.
a) increasing
b) had increased
c) having increased
d) has increased

Answer 1

Hint: The first sentence already tells us the required tense. Look for pointers suggesting which tense to use. The actions are completed in the given sentence. These pointers are indicators of certain tenses.

Complete answer:
 Verbs are words that show action (sing), occurrence (develop), or state of being (exist). Almost every sentence requires a verb. The basic form of a verb is known as its infinitive. The forms call, love, break, and go are all infinitives.
We can discern whether the actions are happening right now by certain pointers that are given in the sentence in the question. So, let us deconstruct the given sentence.
In the first part, the subject is ‘the population of Moscow’. The verb is in the present perfect tense. This means that the action of the population increasing has been populated. So,
naturally, the second part of the sentence will reflect the same tense, as the action is
already completed. So, we need the tense that works with another construction of the sentence, i.e. present perfect continuous tense.

Now, we know what we are looking for. Let’s look at the given options-

a. increasing - This verb matches the given subject, however, this verb phrase is in the present continuous tense. This does not fit into the context of the given sentence. This is not the required answer. So, this is not the correct option.
b. had increased - This verb matches the given subject, however, this verb phrase is in the past perfect tense. This does not fit into the context of the given sentence. This is not the required answer. So, this is not the correct option.
c. having increased - This verb matches the given subject, and, this verb phrase is in the present perfect continuous tense. This fits into the context of the given sentence. This is the required answer. So, this is the correct option.
d. has increased - This verb matches the given subject, however, this verb phrase is in the present perfect tense. This does not fit into the context of the given sentence. This is not the required answer. So, this is not the correct option.
Hence option (c) is correct. 

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