The equation is: C+O2=>CO2
Since we got 10 molecules of CO2 new balanced equation would be 10C+10O2=>10CO2
from this equation we can see that we have 10 molecules of oxygen, however ,we need to find atoms. There are 2 atoms in the oxygen molecule so we need to multiply 10 by 2 which gives us 20 atoms.
The answer: there are 20 atoms of oxygen
The answer is one dot.
The number of dots an element has represented in the diagram, indicates how many valence eletrons( which is the number of electrons in the most exterior energy level of an atom or ion) the element has. So, 1 valence eletron equals one dot.
Explanation:
Copper(II) sulfide reacts with oxygen gas to give solid copper(II) oxide and sulfur trioxide gas.
The reaction is given as:

When 1 mol copper(II) sulfide react with 2 moles of oxygen gas it gives 1 mol of solid copper(II) oxide and 1 mol of sulfur trioxide gas
The gas formed in above reaction that is sulfur trioxide reacts with water to give sulfuric acid or hydrogen sulfate.
The reaction is given as:

1 mol of sulfur trioxide gas reacts with 1 mol of liquid water to produce 1 molo of liquid hydrogen sulfate or sulfuric acid
Distance = 1500m, time = 14min 34.56s = 14*60 + 34.56 = 874.56s
Speed = Distance / time = 1500/874.56 = 1.715 m/s
In order to swim 0.7 miles, 1 mile = 1609.344 m
Time = Distance / speed = 1609.344 m / 1.715 m/s = 938.393 seconds
938/60 = 15 minutes, 38 seconds.
= 15 minutes 38.393 seconds.
I think it’s :answer choice c