The bottom must be 1 by 3 units.
The first and second answer choices has a bottom base of 2 by 2 units.
The third answer choice has a bottom base of 1 by 2 units.
So the only choice that matches the base shown is the last answer choice.
This is also true for the side view.
Both the third and last answer choices match the front view, but only the last one matches them all, so D, or the last/fourth choice, is the correct answer.
Hope this helps!