Which of these sentences uses a reciprocal pronoun?

Ida congratulated herself for finishing her research paper.

One of the vending machines is broken.

Who told Alyssa about the surprise party?

I just love blueberry cheesecake.

At mile 18, the runners encouraged each other to continue on in the race.

At mile 18, the runners encouraged each other to continue on in the race.

Explanation:

Reciprocal pronouns are a type of pronouns that are used when two or more doers (subjects) are behaving in the same manner towards the other and receiving the same outcome simultaneously.

These pronouns are not separate words, but a phrase. Except reciprocal pronoun each other (mostly used when we refer to two people), there is also one another (mostly used when we refer to more than two people).