Why can white not mate in this position from Bobby Fischer Teaches Chess (frame 73)? [Event &quot;&quot;]
[Site &quot;https://www.apronus.com/chess/wbeditor.php&quot;]
[SetUp &quot;1&quot;]
[FEN &quot;6rk/p5p1/1q2Q3/3p4/6P1/8/2b2PK1/4R3 w - - 0 1&quot;]

I'm fairly new to anything more than the basics of chess and I'm currently working through Bobby Fischer Teaches Chess. I came across this on page 96 (frame 73) in which he asks whether white can mate in one move.
I was convinced the white rook could move to H1 to mate. However his answer was &quot;white cannot mate&quot;. Why is this the case?
The bishop on c2 can be moved to h7 to block the check.