Answer: Good thing you provided the image!
Working down the columns:
C base= 2
D base = 4
C height =3
D height = 2
C area = bh = 8
D area = bh = 8
Step-by-step explanation:
Try thinking about drawing a rectangle around the entire image of C and D, connecting each of the corners (sort of like what is being done for B) and then you can perceive the b and h.
The trick to D is to turn your head 90 degrees (or sideways) so you can see those 4 boxes as the base.
For C the base is the 2 boxes, and going up until you meet the other parallel side you can count 4 boxes.
I usually default to using the side which I can easily count boxes as the base and go from there.