问题补充：
Please pass me two---------.
A. pieces of paper
B. pieces of papers
C. pieces paper
D. piece papers
答案：
(答案→)A. pieces of paper
B. pieces of papers
C. pieces paper
D. piece papers
解析：paper做为纸来用是不可数名词，不可数名词本身没有复数形式,如果要表达一定的数量时,通常前面加一个短语做定语,通过定语中名词(很象汉语中的量词)复数来表达，
如: Two cups of water. Three pieces of paper. Four glasses of milk.
