單選題

Ruby: Richard, I haven’t seen you for a month. You look slimmer. Richard: Thanks! You look good too. Ruby: How did you lose weight? Richard: ____________ Ruby: I want to try that too.

 (A) I have been working out in the gym.

 (B) Being on a diet makes me hungry.

 (C) My knees hurt after jogging.

 (D) Exercising is boring.