He fell off the bike and hurt his leg yesterday._______, he had to stay at home for two or three months.
A:So that
B:As a result
C:Such as
D:Because of
P正三角形ABC所在平面外一点,PA=PB=PC=3,且PA,PB,PC两两垂直,则P到面ABC的距离为( )
根据大豆种子的部分结构示意图,回答下列问题.
①蓝藻 ②酵母菌 ③草履虫 ④念珠藻 ⑤水绵 ⑥流感病毒 ⑦葡萄球菌.
下列各式运算正确的是( )