An allosteric activator

ANS:D - both (a) and (c)

The T state of the protein is the Tensed state, when no substrate is bound. T state has low energy and is more stable than are state.

The are state of the protein is the Relaxed state, when substrates are bound. R state has higher energy, thus it is more unstable.

Allosteric activators stabilize the are state, by moving the equilibrium towards the R state, thus increasing the affinity of the enzyme for the substrate.