In which example is credibility used as a speaking tool?
a. the speaker offers a factual basis for an argument.
b. the speaker presents his or her personal qualifications.
c. the speaker appeals to the audience's sense of compassion.
d. the speaker alludes to the importance of the audience's opinion.

the pronoun reference replaces a noun, but you have to make sure there's no room for confusion.

in the first sentence "her" could be referring to shely or to the sister. the answer there is "shelly called her sister and told her about the new baby."

in the second sentence "it" could be referring to the roof or the floor. the answer there is "since the roof leaks on the family room floor, we need to repair the roof."

b. our party quickly made its way into the cave / but we failed to find our host [the cyclops] himself inside.