A:k≤10?
B:k≤16?
C:k≤22?
D:k≤34?
读图区域等高线地形图,下列判断正确的是( )
I have to work with him, because he always makes ____ (care) mistakes.
(Ⅰ)求证:FG∥平面PBD;
(Ⅱ)求证:BD⊥FG.