It is known to us all E-mail is efficient than sending a fax.
A. much
B. many
C. more much
D. much more
网友回答
A. much
B. many
C. more much
(答案→)D. much more
解析：考查比较级。句意“众所周知，电子邮件比传真的效率更高。”根据than可知，应该用比较级，efficient是多音节形容词，比较级借助于more，much可以修饰比较级more。故选D。