Player A: 2-7o

Player B: 5-6o

Board: 4433r

Player A is currently in the lead with two pair, 7 kicker.

If the river is 8 or higher, split pot (both players play the board)

If the river is a 2 or 7, A's two pair is beaten by B's straight

If the river is a 5 or 6, B has a better two pair than A

If the river is a 3 or 4, split pot (both players play the board)

Confirmed this on CardPlayer's calculator. After the turn B has a 27.27% chance of winning, 72.73% chance of a chop.