(____)1. pig pen
(____)2. shop horse
(____)3. when where
(____)4. same Sam
(____)5. March glass
(____)6. sing thin
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( )
用化学用语填空:①2个氢原子____ ②2个氮气分子____ ③2个硫酸根离子____ ④标出氧化铝中铝元素的化合价____