In [722]: df[(df['C']==1) | df['B']]
Out[722]:
A B C
0 1 True 1
2 2 False 1
3 2 True 2
4 3 True 1
In [723]: df.query('C==1 or B==True')
Out[723]:
A B C
0 1 True 1
2 2 False 1
3 2 True 2
4 3 True 1
In [724]: df[df.eval('C==1 or B==True')]
Out[724]:
A B C
0 1 True 1
2 2 False 1
3 2 True 2
4 3 True 1