尿素装置在一定生产负荷下付产蒸汽压力降低时,合成塔反应温度及压力()。
A.升高
B.降低
C.无变化
D.无法确定
参考答案:B
Charli Chaplin____ great contributions _____ the film industry. [ ]
A. took ; to
B. made ; to
C. supplied ; for
D. invented ; for
后牙反的可能病因不包括().
A.乳磨牙早失或滞留
B.后牙区拥挤
C.单侧咀嚼
D.唇腭裂
E.前牙反