What happens if you replace D Flip-Flops with D Latch in a synchronous sequential circuit? 

a. Nothing, it would still work the same. 

b. Instead of a CLK pulse, as soon as the CLK becomes positive, the state transition is done.

c. Instead of a CLK pulse, as soon as the CLK becomes negative, the state transition is done. 

d. The circuit may never stabilize, and will likely produce error.