Cuando se comida chatarra, se de peso.
a.
como, aumento
b.
comen, aumentamos
c.
come, aumenta
d.
comemos, aumenta

C. come, aumenta

Cuando se come comida chatarra, se aumenta de peso.

When junk food is eaten, weight is gained.

Explanation: This is a passive reflexive sentence. In these sentences, the form precedes a third-person verb in the singular or plural, depending on whether the nominal element that appears next to the verb and which is its grammatical subject is singular or plural. Because it is a form of passive, this construction only occurs with transitive verbs: "Cuando se come", direct object is "comida chatarra". "Se aumenta", direct object is "peso". Normally the subject of these sentences denotes something: "junk food", "peso", but it can also denote an indeterminate person.



b.

explanation:

just because.

well, the b sentence is the only one that has sense.