According to the lock-and-key model, the active site of an enzyme has a shape while the induced-fit model describes the active site as shape. According to the lock-and-key model, the active site of an enzyme has a shape while the induced-fit model describes the active site as shape. a. Rigid; nonflexibleb. Rigid and nonflexible; flexible or an adjustablec. Flexible or an adjustable shape; rigid and nonflexibled. Flexible; an adjustable shape

According to the given lock and key model the active site of an enzyme has a Rigid shape while the induced fit model describes the active site as Flexible shape.

Explanation:

Here the model being described is Lock and Key model.

Lock and Key model: In this model the enzyme behaves as Lock and the substrate is as a Key.

So, it mentions that only the right and correct key will fit in the enzyme's active site.

The active sites which are present consists of a specific substrate shape i.e. called as Rigid which only gets reacted with the substrate that perfectly fits into it.

Induced Fit Model: In this type of models enzymes are been considered as flexible and their is a partial role of substrate which determines the final outcome of the enzyme.

it's all four options.