Academic writing is relatively formal. In general this means that in an essay you should avoid the following:

A.colloquial words and expressions (such as "stuff", "a lot of", "thing", "sort of")

B.abbreviated forms (such as "can't", "doesn't", "shouldn't”)

C.two word verbs (such as "put off", "bring up”)

D.asking questions (such as “So why is this?”)

正确答案：colloquial words and expressions (such as "stuff", "a lot of", "thing", "sort of")；abbreviated forms (such as "can't", "doesn't", "shouldn't”)；two word verbs (such as "put off", "bring up”)；asking questions (such as “So why is this?”)