一束带正电的粒子在地球赤道上空竖直向下运动，在地磁场的作用下它将

A．向西偏转

B．向东偏转

C．向南偏转

D．向北偏转

Hypothesis test can be divided into one-tailed test and two-tailed test. A onetailed hypothesis test may not have a:（）

A. "Iess than or equal to" alternative hypothesis.

B. "not equal to" alternative hypothesis.

C. "greater than" alternative hypothesis.