Choose the correct article to complete each sentence below. soy alumno en escuela secundaria americana. a. un c. unos b. una d. unas select the best answer from the choices provided

Option b: una

Explanation: Here we need to complete the sentence:

Soy alumno en escuela secundaria americana.

and the options are:

A. Un  

c. Unos  

b. Una  

d. Unas

The subject here is "escuela secundaria americana", and is easy to see that is feminine and singular.

Then, the right option is b: una, because it is also in the feminine (has an "a" in the last syllable) and is in the singular (it does not end with an s)

Soy alumno en una escuela secundaria americana.