Answer:
A. exercise several hours a day.
Step-by-step explanation:
For those who want to gain weight without accumulating excess fat, the key is to increase weight through gaining muscle mass. For this, it is necessary to practice physical exercises several hours a day that cause a great effort and muscle wear, such as weight training and crossfit, besides having a protein rich diet, such as meat and eggs.
In addition, in some cases protein supplements may be required to increase the stimulation of hypertrophy and accelerate muscle recovery after physical activity.