Correct answer: B:c51...c:b4 2.Rc1# 1...c:d4 2.R:c6# 1.Rd7?? zz 1...c:b4 2.Rc1# but 1...c:d4! 1.Rd8?? zz 1...c:b4 2.Rc1# but 1...c:d4! 1.R:e6?? zz 1...c:d4 2.R