Which sentence shows the author's commitment to informing the reader?

Awhen frightened, a person's heart pumps faster and adrenaline dilates his or her blood vessels.

Bthe surprised children ran around the room like bats circling the ceiling of a pitch-black cave.

Cnews of the tasmanian devil's escape caused adrenaline to pump through the zookeeper's veins.

Dafter walking down the dark alley, the policeman was startled by his own shadow and tripped.