说出我国著名的四大高原?
参考答案:
青藏高原、云贵高原、内蒙古高原、黄土高原
Smoking is one of the ________causes of cancer,killing millions of people each year.
A.major
B.similar
C.commercial
D.chemical
塑料全冠的肩台宽度应为
A.0.5mm
B.1mm
C.可以没有
D.0.3mm
E.2mm