Question

3) Brian _______ on duty today
a) ( ) is b) ( ) are c) ( ) Was d) ( ) am

Answer 1

a(x) is, porque como o sujeito (Brian) está no singular e na terceira pessoa, usa-se o is nesse caso.

Answer 2

Letter A is the correct.

"Brian" corresponds to the third person singular (he), thence the conjugation "is" is the correct for the verb to be