一凸透镜的焦距是50cm，则用该透镜制作的眼镜的度数是 ____
—First, cut up the apples, bananas and pears. And then. . .
I've got the message from Mr. Wang that what he has settled down in Canada.
医生在对患者进行出血化验时，是从前臂的一条“青筋”中抽取血液的．该“青筋”属于的血管类型是（ ）
