If we sunlight a dry leaf with a piece of glass, it may start burning.
A. work; out
B. carry; out
C. focus; on
D. concentrate; on
网友回答
A. work; out
B. carry; out
(答案→)C. focus; on
D. concentrate; on
解析：短语辨析。Work out计算出，锻炼；carry out执行；focus…on…把…聚焦于…;concentrate…on…把…聚焦于…;结合句意可知C正确。句意：如果我们用意块镜子把阳光聚焦于一片干树叶，它很快就会开始燃烧。