A:if it were
B:would it be
C:had it bee
D:should it have bee
甲的质量是乙的质量的5倍,甲、乙两物体分别从10m和20m高处同时自由落下,不计空气阻力,下面描述正确的是( )
In Dalian, it's going to be ____ (sun).
若要使图中平面展开图按虚线折叠成正方体后,相对面上两个数互为相反数,则x+y=____.