What does the word “it” in the first sentences refer to?

Choose the word whose underlined part is differently from the others

Mark the letter A, B, C, or D on your answer sheet to indicate the word that has the underlined part pronounced differently from the others.

Mark the letter A, B, C, or D on your answer sheet to indicate the word that has the underlined part pronounced differently from the others.

Mark the letter A, B, C, or D on your answer sheet to indicate the word whose primary stress is different from the others.

Mark the letter A, B, C, or D on your answer sheet to indicate the word whose primary stress is different from the others.

Choose the word or phrase CLOSEST in meaning to the underlined part in the following sentence.

Alexander Fleming, a Scottish physician –scientist discovered penicillin in 1943.

Choose the word or phrase CLOSEST in meaning to the underlined part in the following sentence.

It is obvious that plastic pollution is a word problem and needs to be quickly resolved.