This pencil is than that one.A. as longB. longestC. longD. longer

问题补充：

This pencil is than that one.

A. as long

B. longest

C. long

D. longer

答案：

A. as long

B. longest

C. long

(答案→)D. longer

解析：句意：这支铅笔比那支长。结合语境可知本句中表示在两个事物中进行对比，故用形容词的比较级，选D。