According to Professor Robert Willis, the study was only possible when______.
A.new types of memory tests had been created
B.the study was led by the United States
C.it gained financial support from rich countries
D.the data were comparable among countries

A.A.new
B.the
C.it
D.the

【参考答案】

D
解析：题干中的According to Professor Robert Willis与该段提到的Dr．Wi......

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