The correct answer is Metal.
Sound waves are vibrations which need medium to propagate. Higher the density of medium, the sound travels fastest. Sound travels fastest in solid than liquid and gas. Therefore, in this question sound will travel faster in metal because metal has higher density than air and water and it will not travel in vacuum as sound needs medium to travel.
B A D C (I think not 100% on this one)
The speed of light in a vacuum is <span>299,792,458 meters/sec, or approximately 300,000 meters/second.
Hope this helps!</span>
I haven't taken biology since my freshman year of high school, so this is kind of a guess. But I know for sure it isn't a solid. So I would go with a gas.
The process is called ovulation