Don't worry about him. He's old enough to __________ himself.
小明自制土密度计并测定盐水的密度.
实验器材:刻度尺、圆柱形竹筷、细铅丝、烧杯、水、待测盐水.
两个内项分别是3和0.8,两个外项分别是x和1.2.