108.
A. be installed as the future form of the verb ‘will’ is missing…..at the beginning of next year tells you that it will happen in the future.
B. will be installing is the active rather than the passive voice and this sentence is in the passive voice. The generator cannot install itself, it has to be installed by someone.
C. going to be installed is incorrect because the is is missing: is going to be installed.
D. will be installed is correct.
109.
A. prevent is incorrect as you need the infinitive of the verb after is used: to prevent.
B. to prevent is correct because it is the infinitive (to+verb) after is used.
C. for prevent is incorrect as for is a preposition and after a preposition you always need a noun or the gerund (which functions as a noun). Correct: for preventing
D. incorrect because the for has been omitted (see C above).
110.
A. which is incorrect as it is a relative pronoun and here you need an adverb of time: when, while etc.
B. why is not correct because it is a question word.
C. how refers to the method of replacing tools and this sentence talks about the time.
D. when is correct because it refers to the occasion when you are replacing the line.