The Great wall is the only one of the buildings on the earth seen from the moon.
A. which is
B. which are
C. that are
D. that is
网友回答
A. which is
B. which are
C. that are
(答案→)D. that is
解析：考查定语从句。当先行词是指物的表达代词，且前面有the only/the last/the very修饰的时候，后面的句子如果使用关系代词，则使用that.本题的先行词one前面有the only修饰，定语从句中缺主语，且one是单数形式，说明后面也应该是单数，故D正确。