Question

ℎ

His colleagues were envious of his success,though he told them not to be that.という文章で正確には最後にthatがついてはいけない理由はなんですか？

Answer 1

ののののの

この文はthatをつかわずにかくと
His colleagues were envious of his success,though he told them not to be envious of his success.
ということだと思います。

to be以下は重複しているので省略されるわけですが、
その場合thatに置き換えたりしないで、
be動詞の場合はそこで終わりになると思います。