下列物质的化学式书写不正确的是( )
A:氧化镁 MgO2
B:氧化钠 Na2O
C:硫酸锌 ZnSO4
D:氢氧化铜 Cu(OH)2
138÷7≈____ 298÷5≈____ 274÷9≈____
——More and more students wear glasses in our school these days.——I agree with you. Students ___ keep on doing eye exercises to protect their eyes.
Look at the picture and answer the questions.
文化是一种精神力量,可以在实践中转化为物质力量。