电除尘的投运及停退与锅炉运行无关，只要锅炉运行可随时使之投入或停止。（）
参考答案：错
30. ---Which hotel are you in?
---I ___ in a hotel. A friend I met on the train from the south___ to put me up for a couple of nights.
A．haven’t stayed; has offered
B．am not staying; offered
C．am not staying; is offering
D．do not stay; offers
滤线栅使用原则中，X线管管电压须超过（）
A.55kV
B.60kV
C.65kV
D.70kV
E.75kV
