The reciprocal pronouns each other and one another are used when two or more subjects in a sentence are also

a. verbs.
b. objects.
c. antecedents.
d. adjectives.

B.objects.

Explanation:

In a sentence the object is where the action falls, for example “Joe is washing the dish”, here “Joe” is the subject, “Wash” the verb and “The dish” is the object, because the action, “wash”, is being applied to it, when the reciprocal pronoun are used is due to the action said in the sentence is being applied from one subject to the other so each become the object of the other. For example, “Joe and Susan love each other” so Joe loves Susan and also Susan loves Joe.