The answer is C I just took this quiz.
Answer:

Explanation:
The ratio of pressure 2 to 1 us 5.48/1= 5.48 rounded off as 5.5.
Referring to table A.2 of modern compressible flow then 
Also
and making
the subject of the formula then
Making reference to
diagram then

There are 6 atoms of oxygen in Ca (NO3)2.
Answer:
-3044.848m/s^2
Explanation:
Initial velocity = 15.7 m/s (u)
Final velocity = -14.444 m/s (v) velocity after striking moving opposite direction.
Time = 0.0099 s
Average acceleration :
change in velocity/ total time
= V - U/t
= -14.444 m/s - 15.7 m/s/0.0099 s
= -30.144/0.0099 s
= -3044.848m/s^2