—Thanks ___________ helping me ___________ my English handwriting.
—You are welcome.
A:for; about
B:to, with
C:for; with
D:with; for
This is my family. Look at the man. ____ (He's/She's)my father.
如图所示边长为a的正方体浸没在密度为ρ的液体中,液体对正方体上表面的压力为Fl,液体对正方体下表面的压力为F2.试在图中作出Fl、F2力的示意图.证明液体对正方体上下表面的压力差△F与正方体浸没在液体中的深度无关.