如图所示，一轻质三角形框架B处悬挂一定滑轮（质量可忽略不计）。一体重为500N的人通过跨定滑轮的轻绳匀速提起一重为300N的物体。（1）此时人对地面的压力是多大？（2）斜杆BC，横杆AB所受的力是多大？
I bought ______ useful dictionary yesterday．_______dictionary is very cheap．（ ）
A．a； AB．a； TheC．an； The
Sometimes you have to stop too much and just go where heart takes you．（ ）
A．thinkB．to thinkC．thinking
Some of my classmates an English play at the art festival two days ago．（ ）
A．haveB．hadC．has
Cao Yinpeng is a 9﹣year﹣old Chinese boy． He is known
saving his father's life．（ ）
A．forB．atC．by
I a shower when Jimmy called me at nine yesterday evening．（ ）
A．am takingB．tookC．was taking
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