Answer: Yo escribo esta carta desde México!
Explanation: We must complete the sentence:
"yo_ esta carta desde México! "
Where the verb is escribir.
The options are
A. Escribo c. Escribe
b. Escribes d. Escribimos
Where the person in everyone is:
a) yo escribo, b) tú escribes, c) el escribe, d) nosotros escribimos.
Because the sentence starst with a "yo", is easy to see that the right option is a.
Yo escribo esta carta desde México!