The correct option is D 700 square feet
The house is made of a triangle and a rectangle.
Area of the house = Area of the triangle + Area of the rectangle
Area of triangle=12×Base×Height
=12×20×10
=100 square feet
Area of the rectangle = Length × Width
= 20×30 = 600 square feet
Area of the house = 100 + 600
= 700 square feet