1.The bus would not have to take the long detour instead of the main highway if the bridge did not become treacherous in the aftermath of an ice storm.
本题是各错综虚拟复合句.
1）if 从句假定的是“如果在冰雹造成的那段灾后时期桥梁没有遭遇危害”,主句假定是“公交车（现在）就不必不走主干道而选择长距离的便道”；
2）did not become 尽管是虚拟语气,但是仅是对现在存在情况的虚拟,但是 in the aftermath of an ice storm 却指的却是过去曾经发生过的事实,因此应该是对过去的虚拟,而对过去虚拟要用 had not become.
2.The seven-month-baby was consider(ed) precocious to her family because she was already able to grasp tiny items dedicately between her thumb and forefinger.
1）本题本来应该是被动语态,但是题目中却把 was considered 写成 was consider,助动词 be 只有三种情况：be done 表示被动,be doing 表示进行,be to do 表示计划好的将来,绝对不存在 be + 动词原形.
2）既然如此,to her family 应该改为 by her family
3）The seven-month-baby was considered precocious by her family 意思是“这个七个月的婴儿被家里人认为是早熟”.