休药期指食品动物从（）到许可屠宰或它们的产品（乳、蛋）许可上市的间隔时间。
A.开始给药
B.停止给药
C.开始好转
D.准备给药
参考答案：B
His luggage includes two large cases which ________ as much as 50kg.
A．weighs
B．is weighed
C．weigh
D．are weighed
放射性源在运输途中不应在（）停留。
A.井场
B.源库
C.公路
D.城镇闹市
