测量误差产生的原因有仪器误差、（）、外界环境。
参考答案：观测误差
Excuse me, Mary, a reporter from Vanity Fair _______ all day. Could you speak to her now?.
A．has been phoning
B．phones
C．has phoned
D．phoned
在采用客户或证券经纪商营业部营业员直接申报的情况下，客户撤单仍须通知场内交易员。（）
