砂轮的旋转运动能切除工件表层的金属,使工件形成新的表面,所以它是进给运动。
参考答案:错
单词拼写, 根据首字母及汉语提示,完成下列单词的拼写,使句意明确,语言通顺。
1. She r_____ (骑)to school on her bicycleevery day.
2. My grandma often gets up e_____ (早)to do exercise.
3. My main t_____ (任务)was to prepare for the meeting.
4. Linda is a s_____ (聪明)and hard-working ,student.
5. He told me to go out to find some s_____ (枝条)for a fire.
甲、乙两种化合物都是含X、Y两种元素,甲、乙中X元素的百分含量分别为30.4%和25.9%,若已知甲的分子式是XY2,则乙的分子式只能是…………( )
A.XY
B.X2Y
C.X2Y3
D.X2Y5