—Sorry, sir. I wasn't there at that time yesterday.
A:how the accident happens
B:how the accident happened
C:how does the accident happen
D:how did the accident happen
如图所示,某人用滑轮先后以甲、乙两种不同的方式来匀速提升重物.如果该人的体重为800N、手臂所能发挥的最大拉力为1000N,滑轮重和摩擦均忽略不计,则以图甲方式最多可提升重为____ N的物体;而以图乙方式最多可提升重为____ N的物体.
①H2O→H+O2 ②ATP→ADP+Pi+能量 ③C3→C6H12O6+C5 ④CO2+C5→C3