I don't know if I completely understand the question, but I believe the answer would be <em>A. Hydrogen gas </em>because the others are compounds that, although may form naturally, aren't pure to begin with. I'm sorry if I'm incorrect. I haven't heard this question worded this way.
This represents that both parents are carriers, but the dominant gene takes over. It is a 25% chance their offspring will receive the recessive gene of colorblindness, which is an example of Bob
Hummingbirds can fly as fast as 60 miles per hour. One reason why its a scientific question is because of their speed. Their speed is very different compared to many other animals. I hope this helps :)
