ANSWER
d. 40 units
EXPLANATION
Method 1
Perimeter is the total distance around the figure.
The perimeter is
[tex] = 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5[/tex]
[tex] = 40 \: units[/tex]
Method 2
The three squares together formed a rectangle with dimensions,
[tex]w = 5 \: and \: l = 15[/tex]
[tex]Perimeter = 2w + 2l[/tex]
[tex]Perimeter = 2(5) + 2(15)[/tex]
[tex]Perimeter =10 + 30[/tex]
[tex]Perimeter = 40 \: units[/tex]
The correct answer is D.