凝结时间的测定试件在养护箱中养护至加水后（）时进行第一次测定。
A、15min
B、30min
C、45min
D、60min
参考答案：B
I would like to join the school volunteer project, and I often imagine _______.
A．what I should do it
B．what should I do
C．what I should do
D．how should I do
关于前臂侧位摄影，错误的叙述是：()
A．尺侧靠近暗盒
B．桡侧靠近暗盒
C．肘部屈曲约90°
D．肩部尽量放低
E．掌面垂直暗盒
