@stewy
which sentence uses a verb that agrees with its compound subject?
a. waiters and waitresses serve the diners at the banquet.
b. cell phones and tablets is powered by tiny batteries.
c. singing or dancing are my aunt's preferred activity.
d. farmers and gardeners plants their seeds in the spring.

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."

yup its an addiction