I'd have to say that the list of choices doesn't go far enough.
Advances in Astronomy have been occurring for at least the past two millennia (2000 years). Maybe longer.
Answer:
The correct solution is "14.6875 kg".
Explanation:
Given values:
Force,
F = 47.0 N
Acceleration,
a = 3.20 m/s²
Now,
⇒ 
or,
⇒ 
⇒ 
⇒ 
⇒ 
Nitrogen isotopes don't have a charge.
The boiling point of water, or any liquid, varies according to the surrounding atmospheric pressure. A liquid boils, or begins turning to vapor, when its internal vapor pressure equals the atmospheric pressure.
Hope this helps. If you need clarification just ask me!