made the model (by) themselves中需要"by"嗎?
1.The children made the model plane themslves還是by themselves?一般句子如"It's made by me"好像是要加by的,為什么用themslves時(shí)不用加呢?
2."There aren't any trees in the garden."中沒(méi)有樹(shù),為什么要用tree的復(fù)數(shù)?還有"There are no seats left.",我看到的往往用seats,對(duì)此我也有和上一句話同樣的問(wèn)題.
3.（由于砍伐）the trees are gone.這句話，不是被動(dòng)語(yǔ)態(tài)，也不是完成時(shí)，卻用"gone"，請(qǐng)問(wèn)這是什么用法？
4.-I'm going to Hainan.-________________.（選擇答語(yǔ)），Enjoy yourself和Have a good trip同時(shí)出現(xiàn)在了備選答案中，若不是，請(qǐng)問(wèn)該選哪個(gè)？有何區(qū)別？