2chまとめスレにあった問題ですが、これの答えって何なんでしょう？

問１　次の英文と同じ意味の英文を選び、選択した英文の番号を解答用紙に書きなさい

That is all man can do

1 That is the only thing man can do
2 All man is able to do that
3 What all man can do is that
4 There is nothing man can't do