Correct answer:

• i4-g4

White had 3 possibilities to recycle pieces:

• on the h1-h6 line,
• on the c7-i3 line,
• and on the a5-i1 diagonal.

The first option was excluded any way (because of Black’s a5-h2;xGe7).

Through playing i4-g4, Black also eliminated the second option, leaving White no other choice than to play i3-d2;x. Black answers with e9-e5 and is sure to capture White’s last GIPF with f1-d2;xGe6.