—_______does your father play tennis after work?
—Every Tuesday and Thursday.
A:How often
B:How soon
C:Where
D:Why
下列几项中对变异在生物学和实践上有重要意义的说法不正确的是( )
如图所示,⊙O中,OA⊥BC,垂足为H,∠AOB=50°,则圆周角∠ADC的度数是( )