Chess Guide for the Intermediate Player/Some basics for openings/Answer for Exercise 1

Nf7 or Nc4	This is a good move, but it's not checkmate - Black can escape to c6. Look for another check...
Qxd7	Yikes - did you notice that Black can capture your queen with his bishop or queen?
Qe6	Yikes - did you notice that Black can capture your queen with his king?
Qf6	Yikes - did you notice that Black can capture your queen in three different ways?
Qg6	This is not a bad move, but it's not checkmate - Black can block the check with his knight or e-pawn. Look for another check...
Nb5	Checkmate! Excellent job! Notice how White is still occupying and controlling the center!
Other move	That doesn't even put Black in check, so how can it be checkmate? Try again...