题干
——This is between you and me. ——I promise. I won't tell others ______you say I can.
A：unless
B：or
C：since
D：and
答案(点此获取答案解析）
A
——This is between you and me. ——I promise. I won't tell others ______you say I can.
A：unless
B：or
C：since
D：and
，重力加速度为g．若接触面间的摩擦力忽略不计，则石块侧面所受弹力的大小为（ ）