It's hard to understand why they would not be affected, whereas dinosaurs were left too crippled to cope, especially if, as some scientists believe, dinosaurs were warm-blooded.
很难理解为什么它们不会受到影响，而恐龙却因为残疾而无法生存，尤其是如果恐龙像一些科学家认为的那样是温血动物。
This lesson is not too hard (for us) to understand.
这课(我们)不难理解。
This lesson is not too hard (for us) to understand.
这课(我们)不难理解。
应用推荐