Listen,someone____(sing)in the classroom.说明考点,
问题描述：
Listen,someone____(sing)in the classroom.
说明考点,
答
Listen,someone is singing in the classroom.
这里要用一般现在时。
答
is singing
答
is singing
考点有两个：
someone不定代词作主语,谓语动词用单数
前面出现Listen,后面用现在进行时