Answer: The last one
Step-by-step explanation: The area of a parallelogram is base x height, so you know the original area of the parallelogram is 2 x 1, which is 2.
Great, so now you have to find the area of the new parallelogram. The question says the base is halved, so the new base is now 1, and the height is quadrupled, so the height is now 4, because 1 x 4 = 4. Plugging that into the equation for the area of a parallelogram, you get an area of 4, because 1 x 4 = 4.
Now, you have to find the ratio between the two areas, and you can see that all the answer choices want the area to be new area:old area. Well, you just solved the new area, and you know the old area, so putting those two in a ratio gives you 4:2. Wait! But you have to simplify it first, or else the answer will be wrong. To simplify, you need to divide both sides by two, since it is the greatest common factor, or GCF. Dividing both sides by 2 will now give you 2:1, which is what the last answer choice says.