正确答案: A

蛋白质

题目：决定柱头与花粉是否亲和的直接物质基础是( )。

解析：A

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举一反三的答案和解析：

[单选题]55_______-

for example

[单选题]According to the last paragraph, it is important to____________.

eat something for breakfast B． be careful about what you eat