Question

A great deal of research _______ into the possible causes of cancer. (Fill in the blank with the most appropriate word.)
A) are being done
B) have been done
C) has been done
D) has done

Answer 1

Hint: Here we have to form a sentence in present perfect continuous tense. A sentence is a meaningful collection of words that has a subject, a verb, and an object. Sentences generally have three basic tenses: past, present and future.

Complete answer:
First, we have to identify whether the given sentence is in active or passive voice. Then we can identify the tense to arrive at the solution. The given question is in passive voice since the subject “possible causes of cancer” is receiving the action of “great deal of research”. Moreover, the performer is absent hence it is a passive voice.

On preliminary understanding, we can see that question is in present tense since research is generally an ongoing process into possible causes of cancer. After considering the options, we can make out the exact form of present tense i.e. present continuous, present perfect or present perfect continuous tense.

Now let us evaluate the options:
Option A) are being done – “are” cannot be used since the action of conducting research is in the singular form. Hence “are being done” cannot be used as action is not in plural form. Thus, The option is incorrect
Option B) have been done – if the subject of a sentence is I – You – We – They or a plural noun (cars, birds, children) we use ‘have been’ to form present perfect tense. In the given case, “research” is a singular form for which we cannot use “have”.As a result, this option is not fit for the sentence. This is incorrect.
Option C) has been done – if the subject of the sentence is He – She – It or a singular noun (car, bird, child) we use ‘has been’ to form present perfect tense. In the given case, “research” is singular so “has been done” is used which represents a passive form of the present perfect tense. This option is correct because it is the best to fit for the sentence.
Option D) has done – it refers to past perfect tense meanwhile research is a continuous process. The question is in the present tense for which this option is not appropriate. This option is also incorrect as “has done” .

Hence Option C is correct. Now, we can frame the sentence, ”A great deal of research has been done into the possible causes of cancer” is the final answer.

Note:
The structure of present perfect tense in passive form is: “has/have been” + past participle. For example – They have been scammed by fraudsters, The assignment has been completed by me.

In order to identify passive voice: Examine what occurred and who was responsible for it.
It's a passive voice if the person or thing responsible for the conduct is either omitted or appears in the sentence after the case and if a past participle appears immediately after the form of "to be".