Answer:
1. Ellos se escriben.
2. Ellos se miran.
3. En el Congreso se habla de política.
4. Ya no se consiguen entradas para el concierto.
Explanation:
In Spanish the pronoun "se" can indicate reciprocity as well as Passive Voice. In sentences one and two, "se" means each other. However, sentences three and four contain Passive Voice. In that respect, the pronoun "se" is used with with the third person singular and plural of the verb to give an impersonal tone. The Passive Voice is also used when the subject who performs the action is not important or is too obvious, and when we intend to focus on the result instead than on who carried out the action.