Fill suitable Modal Auxiliary:
It’s time the government _______ do something about the problem.
A. Should
B. Must
C. Will
D. Can

Hint:Modal verbs are auxiliary verbs which are also known as helping verbs. Will, can, could, must, shall, should, would, may, ought to, might are the different types of modals in English.

Complete answer:
 Modals are used to display whether something that we believe is possible or impossible, certain. We often use them to do things such as talking about capacity, requesting permission, making requests and offers. The root form of a verb having semantic content is usually used after a modal verb. Following a modal verb, the word to does not appear. The word ought to, which is considered a modal verb, is an exception. As a class dependent on some grammatical properties in English and other Germanic languages, modal verbs are distinguished.

Now, let us solve the given question. Option A: 'should' applies to duty or obligation. It refers to the sentence, which states that "it is the responsibility of the government to deal with the issue." Option B: 'Must' is still a duty, but it is far greater than 'should'. 'Must' is used if people are obligated to do something, or if an event will most likely occur. 'Should' instead define a plan or a desired purpose. "Should" is more fitting than "must" within the framework of this sentence, as the sentence applies to an opinion and is significant. The phrase is complete and thus option A is correct and option B is incorrect. Will refers to the future and can refers to a possibility. The word "it's time" gives an opinion, not a future action (will) or choice (can). Hence, both are incorrect.

Hence the correct answer is option ‘A’

Note: You might get confused with the other modal verbs as it seems like all the options might fit in the blank. But to clear your confusions and to find out the correct answer, you can go through the functions of the modal verbs and then select the correct one.