A laser beam can be made narrow enough to () a single cell.A.focus onB.pay attention toC.concentrate onD.lay stress on

A laser beam can be made narrow enough to () a single cell.

A.focus on

B.pay attention to

C.concentrate on

D.lay stress on

正确答案：A
解析：focus on 聚焦;pay attention to，注意，留心;concentrate on，注意力集中;lay stress on 强调。根据句子的意思，应该是光线的聚焦，所以选A。

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A laser beam can be made narrow enough to () a single cell.