When asked why he prefers bikes to buses, the professor said,  “Riding a bicycle takes __________ half an hour, but it’s more convenient and environmentally friendly. ”

A．absolutely

B．accurately

C．approximately

D．exactly

当标准误越小时，下面说法不正确的是（）

A.样本均数的抽样误差越小

B.个体差异越大

C.样本均数和总体均数的差别越小

D.样本均数估计总体均数的可靠性越大

E.样本率估计总体率的可靠性越大