First, calculate the area of the triangle. A=1/2bh. The base is the length of CB (4) and the height is the length from A to the bottom (3):
A=(1/2)(3)(4)
A=6
Now, see which of the choices has an area of 6.
A:
The area of a square is A=s^2. A=4^2=16. 16*2=32
B:
A=4^2=16. 16*(1/2)=8
C:
The area of a rectangle is A=lw. A=4(3)=12. 12(1/2)=6
D:
A=4(3)=12. 12*2=48
C.
Hope this helps!!