首次提出了阶级斗争学说,系统论述了资本主义必然灭亡的理论文献是( )
A:《人权宣言》
B:《共产党宣言》
C:《独立宣言》
D:《资本论》
People usually ________ at home ________ the evening.
——When did you buy this computer? It looks so new.——I it for only a couple of days. My sister bought it for me as a birthday present.
如图所示为初速度v0沿直线运动的物体的速度图像,其末速度为v,在时间t内,下列关于物体的平均速度和加速度a说法正确的是( )