LiuYun's hair is 18 cm. Chen Jie's hair is 4 cm shorter than Liu Yun's. How long is Chen Jie's hair?( )
A:14 cm
B:15 cm
C:16 cm
A.在水平桌面上将天平调节平衡
B.用天平测烧杯的质量记为 m1
C.向烧杯中注入适量的豆浆,用天平测出烧杯和豆浆的总质量记为 m2
D.将烧杯中的豆浆倒入量筒测出体积 V