Which sentence is written in passive voice?
a.
danny finished the construction in a short time.
b.
when he finished the building, everyone admired it.
c.
the new office building was built by my uncle danny.
d.
sometimes, he had to work on the weekends.

C) The new office building was built by my uncle Danny.

Explanation:

Passive voice is a form or set of forms of verbs in which the subject undergoes the action of the object.

Passive voice is used, when;

1: We don't exactly know the subject of the action e.g. A snake was killed. (We don't know, who killed the snake), the trees were cut (who cut them, no idea)

OR

2: When the action itself is more important (want to emphasize action) than subject of the action. For example, A snake was killed by him ( snake being killed is more important or emphasized than who killed the snake).

An easy and short-cut way to identify whether the sentence is a passive voice or not is;

Passive voice always have a form of be (be/is/are/am/was/were) which are followed by third form (past participle) of principal verb. If it is not so, the sentence is certainly not a passive voice. And if it does have this structure the sentence is certainly passive voice.

in that passage i would say the sentence which best describes the overall impact of the setting is when they mention the absence of people because it suggests that taking a walk at night is unusual.