So here we have an example problem that says, after exercising on a hot day, Paula has a red flushed appearance on her face. What caused this? And we've got these 4 potential answer options down below. Now, option A says the heat released from sweat evaporating. Although it's true that Paula is probably sweating a lot after exercising on a hot day, that sweat is not going to create a red flushed appearance on her face.
For that reason, we can eliminate answer option A. As we'll learn moving forward, sweat is a water-based solution and so it is going to be clear and colorless. So, again, it's not going to create a red flushed appearance on her face. Now, moving on, option B says increased oxygen levels in the blood. But when we're exercising, our muscles are actually consuming more oxygen in the blood.
It's very possible that the blood oxygen levels are actually decreased instead of increased as option B suggests. And oxygen itself is a colorless gas and the oxygen levels in the blood are not going to be enough to create the red flushed appearance on her face. And so, for that reason, we can eliminate answer option B. So now we're between either option C or option D, and what you'll notice is option C says vasoconstriction of blood vessels whereas option D says vasodilation of blood vessels. And so, recall that on a hot day when the temperatures are high, our blood vessels are going to dilate. This tells us that vasodilation of blood vessels is going to be the correct answer.
Recall that with vasoconstriction, the "CO" here can remind you that this occurs when it is cold outside. But again, this is a hot day, so we know that it's not going to be vasoconstriction. That's why we can eliminate answer option C and indicate that option D is the correct answer to this example, and that concludes this example, so I'll see you all in our next video.