Some two-movers for you to solve

Here are some two-movers for you to see how easily you can solve them.
White plays, the Black tries to find adequate answer, but in the second move White mates.
You may try sacrifices, checks, anything you can think of, anyway the key-move is unique.
The solution and the comments are visible when you select the area between the brackets [  ].

Problem-770 Nikos Pergialis original

2Qb1B2/1S1sp3/5p2/3pp2B/pp1P2r1/Sk6/1P1p4/K2bRs2 (9 + 13) #2

Solution : [Tries : {1.Sa5+? Bxa5!}, {1.Sc5+? Sxc5!}, {1.Re3+? Sxe3!}, {1.Qc2+? Bxc2!}, {1.Qc3+? bxc3!}, {1.Qc4+? dxc4!}, {1.Qc6? [2.Qxd5#] e6!}, {1.Qc7? [2.Sa5#] Bxc7!}, {1.Qxd7? [2.Sc5# / Qxd5#] bxa3!}, {1.Qxd8? [2.Sa5#] bxa3!} Key : 1.Qc5! [2.Qxd5#] 1…Se3 / Sxc5 / Sb6 / Be2 / Bf3 / Rxd4 / e6 / bxa3 2.Rxe3# / Sxc5# / Sa5# / Qc2# / Qc2# / Bxd1# / Qxb4# / Qc3# Sacrificial key and many tries for careless solvers.]

Problem-771 Emmanuel Manolas Place 8, Asthma-2013, Zagreb

5B1R/3p4/4b3/1s6/7R/5Pk1/6P1/5sK1 (6 + 5) #2

Solution : [Tries : {1.Rg4+? Bxg4!}, {1.Rg8+? Kxh4!}, {1.Bb4? [2.Be1#] Sd2!}, {1.Bc5? [2.Bf2#] Se3!}, {1.Bd6+? Sxd6!}, {1.Bg7?  [2.Be5#] d6!}. Key : 1.Bh6! [2.Bf4#] Bg4 2.Rxg4# In this composition you see the Theme Elmgren, where all the black pieces have defences in the various tries.]

Problem-772 Emmanuel Manolas original

2BS3B/q2b1pK1/3p2p1/2prk3/3R1r2/5P2/3PP3/1Q6 (9 + 9) #2

Solution : [Tries : {1.Sxf7+? Ke6!}, {1.Re4+? Kf5!}, {1.Rxd5+? Kxd5!}, {1.Qe4+? Rxe4!}, {1.Kh6+? / Kh7+? / Kf8+? / Kg8+? f6!} Key : 1.Qf5+! 1…Kxd4 2.Qxf4# 1…Kxf5 2.Rxd5#, 1…Bxf5 2.Sc6#, 1…Rxf5 2.Re4#, 1…gxf5 2.Kxf7# We see a checking key with a queen sacrifice, which can be captured by four black pieces. The interesting thing here is the Anti-triple : Bd7xf5 / Rf4xf5 / g6xf5, where from the three mating moves Sc6 / Re4 / Kxf7 only one is valid after each black move.]