Silman mentions that King and Queen vs. King and pawn on the 7th rank wins, except when it's a flank or rook pawn (and the king is far away from the action, i.e. 6th rank).
The rook pawn case is clear; black king on h1 gets stalemating chances with its pawn on h2.
But the c-pawn and f-pawn case isn't clear to me. Why does King and Queen vs. King and flank pawn on the 7th rank draw?