Answer: The correct answer is graph A.
Explanation:
See Khan Academy.
99% of the earth´s atmosphere by mass is made up of only these elements: Nitrogen and oxygen.
Answer: B) Nitrogen and oxygen.
The refractive index for glycerine is

, while for air it is

.
When the light travels from a medium with greater refractive index to a medium with lower refractive index, there is a critical angle over which there is no refraction, but all the light is reflected. This critical angle is given by:

where n1 and n2 are the refractive indices of the two mediums. If we susbtitute the refractive index of glycerine and air in the formula, we find the critical angle for this case:
Answer:
12.5752053801 m/s

No.
Explanation:
Q = Volume flow rate = 
d = Diameter of pipe = 9 cm
A = Area = 
Volume flow rate is given by

Velocity of fluid is 12.5752053801 m/s
The volume flow rate in m³/s is 
The flow of fluid does not depend on the type of water used. Hence the answers would be same. If Q is constant v will be the same irrespective of the type of water used.