心菲殿下
答案：so，that． 根据句子的设空情况结合第二个设空处后面是一个句子，确定用短语 so…that…，该短语 可以用来引导结果状语从句，意为"如此…以致于…"so的后面加形容词或副词，that后面跟一个从句； 故答案为：so，that
张小小晴晴
1. The problem is too difficult/hard for me to solve.2. The problem is so difficult/hard that I can't solve it.3. The problem is very difficult/hard so that I can't solve it.4. The problem isn't easy enough for me to solve.5. This is such a difficult/hard that I can't solve it.6. This is so difficult/hard a problem that I can't solve it.注：/ 表示可以任意选用其一；还可以把solve改写成work out，solve it改写成work it out.
