The author suggests that the work of Fisher and Hamilton was similar in that both scientists ______.
A. conducted their research at approximately the same time
B. sought to manipulate the sex ratios of some of the animals they studied
C. sought an explanation of why certain sex. ratios exist and remain stable
D. studied reproduction in the same animal species
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在班轮运价表内标示“W/M”表示（ ）。
A. 按货物重量计价
B. 按货物体积计价
C. 按货物质量计价
D. 按货物重量或体积收费较高者计算单位运价
我们通常所说的关税壁垒是指（ ）。
A. 低额出口税
B. 高额出口税
C. 低额进出口税
D. 高额进出口税
This selection is primarily concerned with ______.
A. the eye's adaptation to color
B. the properties of colored surfaces
C. the color of colors
D. the effect of changes in color intensity
The Social Security Act did not include health insurance because the commission considered that its inclusion would jeopardize the passage of the act.
A. evade
B. endanger
C. exclude
D. enhance
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