语法问题：）

星月多多

1。关于比较：
(1)比较的话，在什么情况下要补出谓语动词？以下两例都是主语的比较，可一个补出了谓语动词（大多数情况都是这样），一个没有补出谓语动词。
Local residents claim that San Antonio, Texas, has more good Mexican American restaurants (than does any other city in the United States.) (D-p78-14)
Because natural gas is composed mostly of methane, a simple hydrocarbon, vehicles powered by natural gas emit (less of certain pollutants than those burning gasoline or diesel fuel.) (C-p8-16)

（2）而且为何有时这个补出的谓语动词前置，有时却是正常语序，是否一般情态动词或者不一样时态的的这么处理？这里有讲究吗？
（The pay of senior executives increased in 1990 by a larger percentage than did） the wages of other salaried workers. (C-p67-5)
Inflation has made many Americans reevaluate their assumptions about the future, （they still expect to live better than their parents did）, but not so well as they once thought they could. (B-p80-22)

2。In recent years, prices of common stock have remained high,but,(unlike those of low_related bonds, have not risen) to a level that discourages investors.
我错选了unlike those of low_related bonds,which have not risen。不知问题出在哪儿！这里的but是怎么回事？

3。or也能表转折？eg.  New buildings in earthquake_prone areas must be heavily reinforced, (or they may collapse in a strong quake)[em26]

谢谢：）

zyh79

1。1）如果不添加助动词，会产生歧义，就必须添加。否则，我真觉得可加可不加。
2。but连词，这里连接的是句子,要有谓语。故你的答案错。
   have not risen 的主语是prices of common stock
3。or为otherwize

tongxun

1、我同意zyh79的意见。
第一个中若不加does，意思就变成：San Antonio, Texas has less any other city in the United States 了。意思变了。
第二个：由于those后面有具体的限定词，因此不会引起歧义。若补出助动词，也行。
2、助动词补出的位置可前可后。
3、我同意zyh79的意见。你可以再读一下句子感觉感觉。
4、与zyh79的意见一致。

星月多多

再添一问：）
（1）这里是否省了一个will？
Tiny quantities of more than thirty rare gases, most of them industrial by-products, threaten to warm the Earth's atmosphere even more rapidly over the next fifty years than carbon dioxide will. (B-p162-23)

(2)In Japan elderly people are treated with far greater respect than （they are） in most Western countries. 这里是否可以把括号内的they are省略呢？

tongxun

1、是。
2、可以。若是In Japan 直接跟在than前面，则省略更好。

cook

"简洁" means " 该省就省, 不该省就千万别省" -- 标准: 不导致歧义.
比较中do/does... 省略, 一定是两主语比较, 并且不导致歧义.-- 注意时态不一支, 不可省.

cook

By the way, I like this questions. I copy those questions you uploaded . Thank you very much !

星月多多

hehe~~
谢谢大家：）