The knight's shield serves as weapon AND protectant during battle.

a. adjective
b. verb
c. conjunction
d. interjection

C

Right.

And these...

BEFORE the first day of school, they had only used the computer to play games.

a. adverb
b. preposition
c. adjective
d. conjunction

A

In order to see the double rainbow, the entire class went OUTSIDE.

a. conjunction
b. adjective
c. preposition
d. adverb

A

Are these correct? If I put these choices, I'll be getting three straight adverbs, which is very weird.

Your last two answers are wrong.

B and D?

Yes. Now they are right.

:-)

So, just to make sure... if the last sentence were, "In order to see the double rainbow, the entire class went to the field OUTSIDE," would "outside" be a preposition?

No. Prepositions must be followed by a noun or pronoun object.