在炼钢生产中,造成熔融物爆炸的原因之一是( )。
A.加入炉内及包内的各种原料太干燥
B.氧枪漏水
C.向炉内吹氧
D.车间地面干燥
参考答案:B
Hardly ________ when the flood peak arrived.
A.they had left their village
B.they left their village
C.did they leave their village
D.had they left their village
人造冠龈边缘必须高度磨光的主要理由是
A.美观
B.有利清洁卫生
C.病人舒服
D.加强抗力
E.加强固位