问题
单项选择题
More has been learned about the Moon than any other of the Earth's neighbors in space because of the Apollo program, which enabled men to walk on the Moon and bring back hundreds of pounds of ______.
A．rocks
B．rock
C．stone
D．stones
答案
参考答案：A
解析：[分析] 近义辨析。 stone是最常用词，可指任何石头，rock指岩石，具有可研究价值，可作可数名词，也可作不可数名词，在此应用可数名词的复数。
)有哪些重要特性?