一道SC，语法点区别有些不清楚

Q18:

Antarctica receives more solar radiation than does any other place on Earth, yet the temperatures are so cold and the ice cap is reflective, so that little polar ice melts during the summer; otherwise, the water levels of the oceans would rise 250 feet and engulf most of the world’s great cities.

1. is reflective, so that little polar ice melts during the summer; otherwise,
2. is so reflective that little of the polar ice melts during the summer; were it to do so,
3. so reflective that little polar ice melts during the summer, or else
4. reflective, so that little of the polar ice melts during the summer, or
5. reflects so that little of the polar ice melts during the summer; if it did

能帮忙把里面的语法点说一下吗，谢谢了，还有区别，选对了，可是讲不出道理

我选C

本题考了2个语法点:

1. so...that...的习惯搭配

2. 两个句子并列,第一个句子含有be动词或者become,第二个句子中的be动词或者become必须省略,同时,一些重复的名词或形容词也必须省略。例如:

Once the economic and social usefulness of the motor was demonstrated and its superiority to the horse proved, ... (proved前省略了was)

its superiority to the horse was proved,它对马的优越性得到了证实

it proves helpful这种结构prove主动表被动

这两个句子是不同的

这里应该不是这个语法点，因为temperatures are so cold and the ice cap is reflective这两个BE动词的主语单复数不同，不能随便省吧，个人理解，open to discuss,

这里有个区别我不太清楚otherwise, were it to do so,or else等选项后的区别是什么呢？哪位知道的！！！！！！11

different opinion

I took B as my anser,

I think  "is" can't be omitted when the fisrt be verb is "are"; furthermore, were it to do so is a subjunctive structure that is most logical to fit the meaning of the sentence.

改正一下,应该选B,那个be动词的考点无关,is不能省略的.因为are,is不一样