A:Having not accompanied
B:Not having been accompanied
C:Having not been accompanying
D:Not having accompanied
在不计空气阻力的情况下,下列运动中加点物体机械能守恒的是( )
现有一杯20℃的饱和硝酸钾溶液,欲改变其溶质质量分数,下列方法可行的是( )
x(天)
1
2
3
…
50
p(件)
118
116
114
20
销售单价q(元/件)与x满足:当1≤x<25时q=x+60;当25≤x≤50时q=40+ 1125x .