— Heiscrazyaboutcomputergames. — Itisn't
题型：选择题
问题：
— He is crazy about computer games.
— It isn't surprising _______ he isn't doing well in his study recently. [ ]
A. whether
B. that
C. why
D. what
题型：选择题
| 如图所示，AB是一质量为m的均匀细直杆，A端靠在光滑的竖直墙壁上，B端置于水平地面上，杆身与竖直方向夹角为θ，杆与地面的摩擦系数为μ，保持平衡，则此时杆与地面的摩擦力为（ ） A． B． C． D．μmg  |
mgtgθ
mgsinθ