On Sundays there were a lot of children
题型：选择题
问题：
On Sundays there were a lot of children playing in the park, _______ parents seated together joking.
A．their
B．whose
C．which
D．that
题型：选择题
长方体的木块放在如图甲所示的弹簧上面后，出现了如图乙所示的现象，那么在图乙中木块受到弹簧的__________力，此力的施力物体是____________ 。比较甲、乙两图可以看出木块放上去后，弹簧的长度_______________，说明弹簧同时也受到了_____________力，这个力的施力物体是__________________ 。
