Guys ! i really don’t know how to summarize that（don’t know which part are important to summary). i’m bilingual.
我从中国到美国只有两年，现在就读十年级。

i don't see any right answer. i don't know english and only math

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."

i don't see it in your profile.