Either Chris or the new employee ___ the mail before Dolores or Charles___.

__a.sort; arrives
__b.sort; arrive
__c.sorts; arrives
__d.sorts; arrive

Yes. C is right.

You're welcome.

Both blanks need singular verbs.

he sort?

he arrive?

Those are both plural verbs.

What verb do we use after he?

http://www.grammarly.com/handbook/grammar/verbs/22/verb-forms/

Two subjects joined by "or" are considered singular and need a singular verb.

Thanks