预防沙眼要勤洗（）。
A、澡
B、脸
C、衣服
D、手
参考答案：D
---Mr Wang, I have trouble ________ the text.
---I’m sure you can, but remember ________ it at least three times.
A．to understand; reading
B．understanding; reading
C．to understand; to read
D．understanding; to read
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