A. A girl to sing national anthem is there in the class.
B. The function will end, a girl will sing national anthem at the end of the function.
C. The national anthem will be sung by one of the girls in the class at the end of the function.
D. There is a girl in the class who sings national anthem.
The given sentence contains one of Model verb (Model Verb = will, shall, can, may, might, could, might, must, would). It is in active voice.
Rule :
Subject + Model verb + be + V3 + Optional Objects.