III. Gap Filling One of the (a) Problems facing the world today is global warming. Many scientists believe that the production of carbon dioxide and other greehouse gases is having a heating effect on the atmosphere and this(b) …………. Be very dangerous for human life. We (c)……………….. Examine the problem of global warming and suggest some ways of solving it. a). Bigger b). Biggest c). Big d) most big a) could b) shall c) is d) ought a) may b) can c) should d) must

One of the b) biggest problems facing the world today is global warming.

Many scientists believe that the production of carbon dioxide and other greenhouse gases is having a heating effect on the atmosphere and this a) could be very dangerous for human life.

We d) must examine the problem of global warming and suggest some ways of solving it.

Explanation:

We can fill in the blanks by eliminating the options that are not usable. For the first sentence, the options were: a). Bigger b). Biggest c). Big d) most big. When expressing this type of idea or thought, it is common to use the superlative form of the adjective. For example: one of my greatest fears is... Therefore, the best option is letter b) biggest. It is the correct superlative for the adjective "big".

For the second sentence, the options were:  a) could b) shall c) is d) ought. Since the word right after the gap is "be", we can eliminate letter c) is. We can also eliminate letter d) ought, because it needs a "to" after it, which we do not have. Finally, let's pay attention to the words' meanings. "Shall" affirms that something is or exists, while "could" makes it clear that something is a possibility. Since we are not sure of what shall be, the best option is a) could.

For the third sentence, the options were a) may b) can c) should d) must. The previous sentence said it was possible for the heating effect to be dangerous for human life. If something is dangerous, we have to study it. In other words, we "must" study it. After all, our lives depend on it.

buy a huge library full of all the books ever written

answer: do

the 'italicized phrase' is a noun clause that is used as a direct object.