When the difference in weir crest and downstream river bed is limited into 3 metres, the weir, generally used is

When the difference in weir crest and downstream river bed is limited

1.	When the difference in weir crest and downstream river bed is limited into 3 metres, the weir, generally used is
A.	vertical drop weir
B.	drystone slope weir
C.	concrete slope weir
D.	parabolic weir
Answer» D. parabolic weir