In the lock-and-key model of enzyme action, the fits into the of the enzyme.
a) product; substrate.
b) active site; product.
c) substrate; active site.
d) active site; substrate.

In the lock-and-key model of enzyme action, the ___ substrate fits into the __active site of the enzyme.
This model was proposed by the Emil Fischer in 1894 and proposed that enzymes have different shape and proposed lock and key model
so i conclude option C is correct
hope it helps