A:森林面积减少
B:生态保护
C:环境污染
D:生物入侵
选用所给的单词或词组填空。
candy, bowl, short, luck, beef and potato
— Did you notice her enter the office just now?
— No, I ____ (repair) my computer all the time.
如图所示,穿在一根光滑的固定杆上的个小球A,B连接在一条跨过定滑轮的细绳两端,杆与水平面成θ角,不计所有摩擦,当两球静止时,OA绳与杆的夹角为θ,OB绳沿竖直方向,则正确的说法是( )