You can not play table tennis by yourself.

　　你不能獨自一個人打乒乓球。

　　I have to inform you that we can not approve of it.

　　我不得不告訴你，我們不能批準(zhǔn)它。

　　The sweet potato in the village is what I can not forget.

　　山村的地瓜是我不能忘懷的。