皮内注入结核菌素后经多长时间观察结果
A．12～24小时
B．24～48小时
C．48～72小时
D．3～4天
E．4～5天
参考答案：C
A(n)_______ of 10,000 dollars was _____ to anyone who could provide any clues leading to the
catch of the criminals who tried to murder the president. [ ]
A. award; offered
B. reward; given
C. prize; provided
D. reward; offered
由于减小吸入管的阻力损失可以防止汽蚀现象的产生，则对吸入管的要求是（）。
A、直径大
B、直径小
C、直径变化率小
D、直径变化率大
