问题描述：
How pleased the detective was ______what his customer told him．
A．hearing B．hear C．heard D．to hear
答案d为什么选to do?还有帮忙分析依句子结构
A．hearing B．hear C．heard D．to hear
答案d为什么选to do?还有帮忙分析依句子结构
问题解答：
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