It violates the dormant commerce clause is the best argument for the out-of-state growers who wish to challenge the new law.
Option a
Explanation:
The dormant commerce clause states that any state must not discriminate between other state's commerce systems or competitions. This clause also limits the power that individual states have on these matters. It is used by the judiciary to overturn the "state regulation of commerce and trade".
In recent years, the dormant commerce clause has been a subject of resurgence of both scholarly and judicial concern. In the given example, the state passing a law to limit the introduction of out of state grown apples violating the "dormant commerce clause" for which the out of state apple growers can challenge the new law which has been imposed by the new state.