2013年托福词汇精选试题及答案20

1. The woolly mammoth, a long-haired rhinoceros, and other mammals have been periodically exposed in the tundra of Siberia, the hair and red flesh still frozen in cold storage.

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

(A) photographed

(B) uncovered

(C) located

(D) preserved

2. A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetation, or materials adversely.

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

(A) negatively

(B) quickly

(C) admittedly

(D) considerably

3. 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

4. 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

5. 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