Fill in the blank (3): en español, "to pick up" el auricular es cuando estoy en la calle, uso el . yo termino la conversación y auricular.

1. En espanol, "to pick up" el auricular es recoger el auricular.
This sentence basically means to pick up the phone. Auricular means headphone, but it is referring to those old-school landline phones that people used to use in the past. However, the idiom remain in use in the Spanish language.

2. Cuando estoy en la calle, uso el telefono celular.
This sentence means - When I'm out in the streets, I use my mobile phone. El telefono is a telephone, and celular is cell, so telefono celular is a cell phone. Given that this person is not home, they cannot use their landline phone.

3. Yo termino la conversacion y cuelgo el auricular
Colgar el telefono/auricular means to hang up, stop having a conversation over the phone. Given that the verb colgar is irregular, there is a specific way to conjugate it which has to be learned by heart - cuelgo, cuelgas, cuelga, colgamos, colgais, cuelgan.

The answer is a but you could also use c if you want