a. Guarding is better at first glance but Re5 instantly shows the guard will fail.
b. White wins it is a 4 vs 2 pawn at queenside with abc connected pawns
c. cxb5 followed by Kd7
d. White is winning as white king / bishop can join in the attack
e. d-pawn sacrifice? eye on a6.
f. (e ii?) Assume d-pawn sacrifice is correct, the only move is Bd2.
Here is more materials to practice your endgame calculation skills on!
1a. Evaluate the following position with black to move. Who is winning, or is this a draw? Should black take on f4 or guard his own pawn on c5?
1b. A few moves later, this position was reached, once again with black to move. Who is winning here, or is this a draw?
1c. A few more moves later, this position was reached. Black has one move here that holds equality, while all other move loses(!). Find this move, and try to find the best plan for black to create a fortress:
1d. Again, evaluate this position. Who is winning, or is this a draw?
1e. White has just played Kg3??, blundering away all his advantage. Black must find the only move to hold the draw. What is this move?
1f. Black has just played the losing Ka6??, and white is completely winning if he finds the only move (once again). Find this move for white:
Hope you enjoyed those and found them helpful. Here is the game (I was white) where all of those position came from: https://www.chess.com/game/live/45435608321