
Solution

1… Qxb2 wins the rook since 2. Qxb2 allows Nd3+, followed by Nxb2.
Note 1… Nd3+ 2. Qxd3 Qxb2+ would also be good but wins less material than 1… Qxb2
1… Qxb2 wins the rook since 2. Qxb2 allows Nd3+, followed by Nxb2.
Note 1… Nd3+ 2. Qxd3 Qxb2+ would also be good but wins less material than 1… Qxb2