A:turned; have scored
B:turned; had scored
C:had turned; have scored
D:had turned; had scored
下列句子中标点符号使用不恰当的一项是( )
30+40-20=____
5+60-5=____
90-50-40=____
为了探究压强大小跟哪些因素有关,老师准备了如图所示的器材:①用钉子做腿的小桌、②海绵、③砝码、④木板、⑤盛有适量水的矿泉水瓶⑥装有沙的容器等供同学们选择,同学们所选的四组器材中,不能达到探究目的是 ( )