田间喷洒有机磷农药时发生中毒最主要原因是()。
A.呼吸道吸入有机磷农药
B.皮肤污染
C.通过污染的手拿食物经消化道摄入
D.体质虚弱
E.以上都不是
参考答案:B
在世界80多个黄金生产国中,占世界查明黄金资源量和储量基础最大的国家是()。
A.中国
B.美国
C.南非
D.俄罗斯
An analyst does research about correlations and gathered information about three economic variables. He noted that whenever variable X increased by one unit, variable Y increased by 0.5 units but variable Z decreased by 0.5 units. The correlation between variables X and Y and the correlation between-variables X and Z, respectively, are closest to:()
A.A
B.B
C.C