问题
单项选择题
If you（）bright sunlight（）dry wood with a glass, it will start burning.
A.expose；to
B.concentrate；on
C.aim；at
D.focus；on
答案
参考答案：D
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If you（）bright sunlight（）dry wood with a glass, it will start burning.
A.expose；to
B.concentrate；on
C.aim；at
D.focus；on
参考答案：D