关于比较结构求帮助

橙圆

PREP08 1  第212题

212. (GWD-10-Q1)

According to a survey of graduating medical students conducted by the Association of American Medical Colleges, minority graduates are nearly four times more likely than are other graduates in planning to practice in socioeconomically deprived areas.

A.       minority graduates are nearly four times more likely than are other graduates in planning to practice

B.       minority graduates are nearly four times more likely than other graduates who plan on practicing

C.       minority graduates are nearly four times as likely as other graduates to plan on practicing

D.       it is nearly four times more likely that minority graduates rather than other graduates will plan to practice            (C)

E.        it is nearly four times as likely for minority graduates than other graduates to plan to practice

此处A选项解释

A.     主系表结构的比较中，如果是主语比较，系动词要省略，are多余；be likely in doing用法错误，应为be likely to do...

再看这题
216. (T-3-Q39) (天山-7-39, OG12-18)

Plants are more efficient at acquiring carbon than are fungi, in the form of carbon dioxide, and converting it to energy-rich sugars.

A.       Plants are more efficient at acquiring carbon than are fungi,

B.       Plants are more efficient at acquiring carbon than fungi,

C.       Plants are more efficient than fungi at acquiring carbon,

D.       Plants, more efficient than fungi at acquiring carbon,      
E.        Plants acquire carbon more efficiently than fungi,

A.     Than后面需要补出are，否则有acquiring fungi的歧义；后面的in the form of carbon dioxide错误的修饰了fungi；converting应当与acquiring平行

此处A句也为主系表结构。但省略系动词are会出现歧义。

在此求解。什么时候改省什么时候不改省？