What distinguishes shareware from freeware?

The distinguishing feature between shareware and freeware is that shareware typically requires some form of payment after a trial period or while offering full access to its features, while freeware is entirely free to use without any payment obligation. The key aspect of shareware is that it might provide the software on a trial basis, allowing users to evaluate it before deciding whether to purchase.

Regarding the other option about freeware not being modifiable, while it's true that freeware often comes with restrictions on modification, this characteristic doesn't define what distinguishes shareware from freeware. Freeware can indeed vary in terms of what is permissible regarding modification, but shareware primarily concerns the payment and usage rights.

Therefore, identifying the correct distinction revolves around the payment model associated with shareware as opposed to the free access of freeware.