Children are . . . . . . . . school. A. at B. in C. of D. on

The correct answer is: B. in

The preposition “in” is used to indicate a location inside a place or object. In this case, the children are inside the school building.

The other prepositions are not correct in this context.

• The preposition “at” is used to indicate a location at a specific point or place. In this case, the children are not at a specific point in the school building.
• The preposition “of” is used to indicate possession or association. In this case, the children are not associated with the school building.
• The preposition “on” is used to indicate a location on a surface or area. In this case, the children are not on the surface of the school building.