无框眼镜不应存在因螺丝旋得过紧而引起的严重应力,用()检查。
A、顶焦度计
B、曲率计
C、偏光仪
D、偏光应力仪
参考答案:D
—Look at the sign on the wall.
—Oh, smoking ______ here.[ ]
A. doesn't allow
B. didn't allow
C. isn't allowed
D. wasn't allowed
简述HCG的来源、生理功能和应用。