Four puzzles in one

Four puzzles in one, composed by Werner Speckmann, 1963. In each case, White to play and mate in two. (a) As in diagram; (b) In (a), move Qh7 to a7; (c) In (b), move Ke6 to c6; (d) In (c), move Ke4 to c4. We regret that there is no prize for this puzzle, owing to the Christmas printing schedule.

Last week’s solution 1 g4!! blocks the c8-h3 diagonal, so a back rank mate with 2 Rc8+ is threatened. In defending the threat, Black loses the queen.
Last week’s winner Ian Renshaw, Penryn, Cornwall