1. Servió
2. Pedimos
3. Pedistes
4. Pedí
5. Servió
6. Pidió
El is singular and masculine and los is plural and masculine while la is singular and feminine and las is plural and feminine.
I hope you have the idea now.
In Spanish all things have a gender is a little confusing.
D.Perezoso
A,B & C fall in the same group