北京新航道致力于为广大考生提供托福培训以及托福考试资讯。近些年来，托福考试越演越烈，家长都希望送孩子出国深造，为了将来的发展和自身的锻炼。托福考试也几经变革，但是总也离不开听说读写几个部分。其中，词汇是基础，贯穿于始终，是一门语言的敲门砖，掌握好词汇是托福考试的步。为了地帮助考生记忆词汇，北京新航道小编为大家整理汇集了一些词汇练习题，正所谓实践出真知，希望大家在做题的过程中加强对词汇的理解和掌握。

　　193. As the Earth developed, the concentrations of these pollutants were altered by various chemical reactions; they became components in biogeochemical cycles.

　　The word "altered" is closest in meaning to which of following?

　　(A) eliminated

　　(B) caused

　　(C) slowed

　　(D) changed

　　194. The result is an increased concentration of noxious chemicals in the air. The concentrations at which the adverse effects appear will be greater than the concentrations that the pollutants would have in the absence of human activities.

　　The word "noxious" is closest in meaning to which of following?

　　(A) harmful

　　(B) noticeable

　　(C) extensive

　　(D) weak

　　195. The actual concentration need not be large for a substance to be a pollutant; in fact the numerical value tells us little until we know how much of an increase this represents over the concentration that would occur naturally in the area. For example, sulfur dioxide has detectable health effects at 0. 08 parts per million (ppm) , which is about 400 times its natural level.

　　The word "detectable" is closest in meaning to which of following?

　　(A) beneficial

　　(B) special

　　(C) measurable

　　(D) separable

　　196. The acute, growing public awareness of the social changes that had been taking place for some time was tied to tremendous growth in popular journalism in the late nineteenth century, including growth in quantity and circulation of both magazines and newspapers.

　　The word "acute" is closest in meaning to which of following?

　　(A) useful

　　(B) intense

　　(C) genuine

　　(D) controversial

　　上面是几道词汇题，大家都会了么?其实词汇掌握并不难，通过做题是的方法。在语境中体会词汇的用法才能掌握的更牢靠。祝大家取得好成绩。

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