✨ ベストアンサー ✨
⑴(english /it /necessary/study/is/to)every day.
It is necessary to study English every day.
⑵(better/I/to/it/think/agree)to their proposal.
I think it better to agree to their proposal.
⑶He (answer/the question/to/it/hard/found).
He found it hard to answer the question.
It is important never to give up.
⑸It is (not/answer/impolite/an e-mail/to).
It is impolite not to answer an e-mail.