Four-Year-Old Lupe Enters His Parents' Room While They Are Having

Four-year-old Lupe enters his parents' room while they are having sex. What should his parents do in this situation?

A) lunge for a towel to cover up first and then scold him for barging in
B) gently remind Lupe that they would like their privacy at that moment
C) react very matter-of-factly and tell Lupe that it is "grown-up time"
D) ignore Lupe and continue the act because he is too young to understand