11. "One check and one threatening to checkmate" is a draw.
(See example in Diagram 11 and 12.)

Diagram 11: Red moves first

R4=2 k5=6
R2=4 k6=5
R4=2 k5=6
R2=4 ...

Explanation:

Because perpetual threatening to checkmate is a draw, one
check and one threatening to checkmate should be a draw too.

Diagram 12: Red moves first

C4=5 k5=6
C5=4 k6=5
C4=5 k5=6
C5=4 k6=5
C4=5 ...

Explanation:

After Red's C4=5, Red can R7=5 g4+5 R7+2 c4-2 R7=6 k5=4 N7+8 k4=5 N8-6
k5=6 C5=4 g5+6 P4+1 to checkmate. Therefore, this is an example of
one check one eventually checkmate. It should be ruled as a draw.