There _________ lots of healthy food on the table.[ ]
A. have
B. has
C. are
D. is
答案:D
管形母线的补强衬管的纵向轴线应位于焊口中央,衬管与管母线的间隙应小于()mm
A.0.1
B.0.3
C.0.5
D.1
炼焦用煤由什么构成?