A:硝酸铵溶于水吸收大量的热,食盐溶于水也吸收大量的热
B:氮肥氯化铵与碱研磨可放出氨气,氮肥尿素与碱研磨也能放出氨气
C:盐酸与块状石灰石反应能制取CO2,则稀硫酸也能与块状石灰石反应制取CO2
D:氢气与空气混合点燃可能爆炸,CO与空气混合点燃也可能爆炸
87+78=____ 65+56=____ 34+43=____ 54+45=____
87-78=____ 65-56=____ 43-34=____ 54-45=____
— Does your son ________an hour ________ his homework after school?
— No, shorter than that now, about half an hour.