padi IDC dive theory – Physics

Q3
A scuba tank is contaminated with 2% carbon monoxide. If you were to dive with it at 20 meters what would the equivalent affect be?
c.) 6%

Q4
Underwater it is difficult to determine where a sound comes from because sound travels  _____ times faster in water because water is ___________ than air.
a.)   4 / colder
b.)  4 / warmer
c.)   4 / denser
d.)  2 / denser