单选题 Heat exhaustion is a condition caused by ______to sunlight or another heat source which often results in dehydration and salt depletion.

A.a reaction to
B.overexposure
C.a limitation of
D.an absence of

【正确答案】 B

【答案解析】[解析] B选项overexposure(过度暴露)符合题意，如：Don't overexpose the children to television．(不要让孩子长时间看电视。)A选项a reaction to(反应)、C选项a limitation of(局限)、D选项an absence of(缺乏)都不正确。本题空格处是说由过度暴露在阳光下引起的。因此B选项为正确答案。