为什么Mars is not an easy place to live on而不是to live?求老师们详细的语法讲解,

为什么Mars is not an easy place to live on而不是to live?求老师们详细的语法讲解, mars is not,it seems,the dry old planet we once believed it to be.为什么believe后面要用it to be?我选it错了. 初二英文句子填空A:Some scientist ______(send) a spacecraft to Mars.And it______(reach)Mars.B:Really?What_____we_____(discover)?Is there life on Mars?A:No.We______(not find) any life on Mars yet. 为什么 the excitement of being on Mars is worth it 中要有being,没有不行吗?但我还有一个问题，例如：a feeling of being uncertain about something or not 中的being也是这个用法吗？ 为什么bruno mars这么火? space ——(fly)to Mars is very interesting fly的适当形式为什么选择flight Is there life on Mars(火星)?We do not know.We are sure that earth people like us cannot live on Mars.Earth people need oxygen（氧气）to breathe(呼吸),but there is almost no oxygen on Mars. Living on Mars is like living on a very high mountain 火星不是一个容易居住的地方是Mars is not a easy place to live on 还是to live live in Mars还是live on Mars 为什么 It is not a peach.It's an什么?A orange B appleIt is not a peach.It's an什么?A orange B apple 为什么选择A French is not an easy language to learn.为什么结尾要用to learn?简说 there is __ egg at home.能添not an么?为什么 为什么VideoConverter转RMVB时,出现This file is not an effective media file NOVA IS THERE LIFE ON MARS怎么样 This Is Not An Exercise 歌词 This Is Not An Exit 歌词 This is not an orlginal copy of money is not an object翻译