1.We will have to stay at home if it isn't fine tomorrow.
答案：isn't fine / doesn't be fine （前者应该是最佳答案）
2.A What great Olympic Games (China has held)!
3.A You don't need to worry a lot.= You needn't worry a lotWe will have to stay at home if it______ fine tomorrow.Adoes not be Bis not be Cis not因为后面是形容词，如果有行为动词，才会借助助动词 do,does 或did呢。除非是祈使句如：Don't be shy. 别害羞。If it doesn't rain tomorrow, I'll play football with my friends.What will you do if it is fine tomorrow?