A. There's a ticket machine the entrance. B. She spent the day sunbathing The swimming pool

C. There are always flies the kitchen ceiling

A) at

B) in

C) on

Explanation:

Prepositions usually comes before a noun or pronoun. There are three types of prepositions.

i) Preposition of place or position such as  on, between, behind, in front of, opposite, in, at, below, above and so on

ii) Preposition of time and date such as by, from, before, in, on, at, since, for and so on

iii) Preposition of Travel and movement such as across, along, from, at, to, up, down and so on

A. There's a ticket machine at the entrance.

B. She spent the day sunbathing in The swimming pool

C. There are always flies on the kitchen ceiling

i think the answer is c