Question

The first half of the play was so long that I went outside - the intermission for some air.
(a) while (b) during (c) how (d) since.​

Answer 1

b) during

The blank needs to be filled using a preposition.

'How' is not a preposition. Also, the sentence is a simple statement and is not posing a question. Therefore, 'how' is not the right option here.

The other three options are prepositions. However, looking at the rest of the sentence, only one option fits the bill (without changing the present sentence), which is b)during.

-Option a)while could have been used if the sentence was:

The first half of the play was so long that I went outside while the intermission was on. (New sentence structure)

-Option d)since could have been used if the sentence was:

Since the first half of the play was so long, I went outside during the intermission for some air.(New sentence structure)

However, here too, one would have to use 'during'.