I'm not 100% sure, but I believe what you mean is when they eject the old propulsion motors. Yes, they land in the ocean and the US Navy retrieves them for later use.
Answer:
water
Explanation:
coz out of the choices water is the only one that is not an element.
water formula is H2O
20km every 1 hr is what 20km/hr means.
so 3hrs is 20km*3=60km.
Density is directly proportional to mass. So if there's less matter inside object, its density will also reduce.
