You just did use a sentence.
Answer: B
All of them are run on sentences! Hope this helps :)
A reciprocal pronoun is a pronoun which is used to indicate the number of people that are executing a particular action.
There are two types of reciprocal pronouns, they are 'each other and one another'. Each other is used when the action executed is carry out by two people and one another is used when the action executed is carry out by three or more people.
The answers to the above questions are as follows:
1. Alex and Martha say goodbye to EACH OTHER.
2. The puppies playfully bit ONE ANOTHER on the nose.
3. The mom and dad love EACH OTHER very much.
4. The children fought with ONE ANOTHER on the playground.
