The words that can refer to a boy but not to a girl from your list are "bailarín" and "atleta" in the masculine form. "Bailarín" specifically refers to a male dancer, while "atleta" can be used for both males and females, but in its masculine form it specifically refers to a male athlete.
However, "joven" is gender-neutral and can refer to both boys and girls, and "cantante" is also used for both genders.
So, the best answers are "bailarín" and "atleta" (when specifically referring to males).