Question

My sister ... busy at three o'clock, so you can call back at that time

a' will
b,won't be
c , will be

Answer 1

É a alternativa letra c

Answer 2

My sister won't be   busy at three o'clock, so you can call back at that time  

(minha irmã não estará ocupada as 3 horas, então vc pode retornar naquela hora)

a' will

b,won't be  (resposta)

c , will be