The headmaster has decided to make school uniform. What is your opinion about compulsory school uniform at school? Why is it good or not good?

it is good

Explanation:

why is because it's easy to identify the school

the statement flat characters usually only have one trait that is developed in their story lines is true.

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."