用碗扣式钢管脚手架可搭设双排外脚手架，拼拆快速省力，但不可搭设曲面脚手架和高层脚手架。（）
参考答案：错
现有一圆心角是90°，半径是8cm的扇形纸片，用它恰好围成一个圆锥的侧面（接缝忽略不记），则该圆锥底面圆的半径为 （ ）
A．4cm
B．3cm
C．2cm
D．1cm．
Compared with his sister, Jerry is even more ___to, and more easily troubled by,emotional and
relationship problems. [ ]
A. skeptical
B. addicted
C. available
D. sensitive
