将一直角三角板和直尺如图摆放,则∠1+∠2等于( )
A:30°
B:60°
C:90°
D:180°
If we spend too much time on the Internet, we won't have enough time to study. , working on computers too long may cause headaches or sore eyes.
所有的细菌都有细胞壁、芽孢、鞭毛及荚膜,而都没有成形的细胞核。(判断对错)
流出肾脏的血液成分与流入肾脏的血液成分相比,其特点是( )