She always ____________ Chinese at home. [ ]
A. says
B. talks
C. speaks
D. talk
答案:C
青铜文化是我国的民族瑰宝,历史悠久,其光辉灿烂的历史在
A.原始社会末期
B.夏朝
C.商朝
D.西周
如图,用轻绳将小球悬于O点,力F拉住小球使悬线偏离竖直方向60°角,小球处于平衡状态,要使F有最小值,F与竖直方向的夹角θ是( )
A.0°
B.30°
C.60°
D.90°