(单选题)

Before the study, which of the following was unclear?

A.Whether babies know objects are gone.

B.Why babies were interested in what was hidden.

C.What made babies remember objects’ existence.

D.Whether babies can remember what was hidden first.

参考答案：C

参考解析：

细节理解题。根据第一段中的最后一句话“But it was still unknown what babies needed to remember about objects in order to remember their existence.”可知，在研究之前，科学家们不知道什么使婴幼儿记住一种物品的存在。故选C。

知识点：