The workers were made from morning to night in the past.
A:worked
B:to work
C:work
D:working
既是正数又是分数,这样的数是什么数,举两例说明.
如图所示是实验室制取气体的常用装置,请根据要求回答问题:
把6﹣(+3)﹣(﹣7)+(﹣2)写成省略括号的形式应是( )