175-Mate in two SOLUTION.

Solution: 1. Bg6! waiting
 1... Rb8/a8/d8/e8/f8/g8/h8 2. Sxc7#
 1... Se8 [a] /g8 [a] /d7 [a] /h7 [a] /e4/g4 [b]  2. B(x)e4 [A] #
 1... a4 2. Sb4#
 1... Se3/b2/f2 2. S(x)e3#

174-White mates in two SOLUTION.

Solution: 1. Be2! waiting
 1... Bg6+/g8 2. S(x)g6#
 1... fxe5 2. Bg5#
 1... c3 2. Sd3#
 1... Se3/g3+/d2/h2 2. B(x)g3#

173-White mates in two SOLUTION

Solution: 1. Bb8! waiting
 1... e5 2. Rxd6#
 1... Ke5 2. Rxc5#

172-White mates in two SOLUTION.

Solution: 1. Se5! [2. Rd7, Sf7#]
 1... Bc6 2. Sf7#
 1... Bxd5 2. Rd7#

171-Mate in two SOLUTION.

Solution: 1. Sc6! [2. Re7, Sd4#]
 1... Qf8/e8/h4/f6 2. Sd4#
 1... Qd8/xe5 2. S(x)d8#
 1... Qh7/g7 2. Sd8/d4#
 In this problem, at least one mate in the set play is changed following the key. This maneuver is called MUTATE