¿tú a california, no?
a.
fuiste
c.
fue
b.
fuimos
d.
fui

A. Fuiste. Tú fuiste a California, no?

¿Tú fuiste a California, no?

Why?
B. Fuimos means "we went", when the question is asking if the person went, not the person and them.

C. Fue would be correct, but since it's asking ''Tú" and not "Usted", it is incorrect.

D. Fui is what the person would ask if they did go to that destination, Example: "Si, yo fui a California,"

This is how we get our answer, A. fuiste, because it is directing it to the person and it is understanding with the use of words.

Hope this helps!~