Zimbabwe's government policies have actually helped neighbouring countries in one way.
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苯的爆炸极限(V/V%.)是()。
A. 8.0～12.0
B. 8.0～42.0
C. 1.2～1.9
D. 1.2～8.0
That fire ants prey on bollworms and budworms is mentioned to show that
A. pests often attack each other to maintain a balance of nature.
B. fire ants are not always harmful pests in given situations.
C. fire ants are stronger and fiercer than bollworms and budworms.
D. pests are either harmful or beneficial to people or plants.
The author's tone in talking about fire ants in the US seems to be
A. critical.
B. indifferent.
C. fearful.
D. objective.
Which of the following statements is NOT tree？
A. Many medical journals also publish online.
B. A few medical journals are general medical journals.
C. Most medical journals publish only online.
D. Most medical journals are specialty journals.
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