Answer:
What does a turntable built into a track look like?
Step-by-step explanation:
Let us go through all the choices one by one:
Choice A: What did the turntables built into the track allow?
The excerpt already tells us that <em>"Turntables built into the track allowed the carts to be shifted about in any direction." </em>
Therefore this question is already answered and there is no need for an illustration.
Choice B: How were dump carts raised to designated floors?
The excerpt already tells us that <em>"This enabled the material to
</em>
<em>be moved from the truck at ground level onto dump carts,
</em>
<em>raised by elevator to the designated floor, wheeled onto the
</em>
<em>track, and moved quickly to the exact spot needed."</em>
So we already know that the dump carts were raised to the designated floors by elevators, and therefore there is no need for an illustration.
Choice C: When was a track system installed on a floor?
An illustration is pictorial; it can only give us information that be represented by pictures or diagram. An illustration cannot give us temporal information.
Choice D: What does a turntable built into a track look like?
The except only tells us that <em>"Turntables built into the track allowed the carts to be shifted
about in any direction."</em> It does not tell us how do these turntables look like.
Therefore, an illustration will tell us how does a turntable built into track look like. And an illustration is the only way this question can be answered.