Answer;
-Gases
Explanation;
-Pressure can affect the density of gases.
-Density of gases changes with pressure and temperature because gases are compressible fluid and because they are compressible, when pressure increases molecules come closer to each other which means increase in density and when pressure drops molecules of gases become free to expand and get away from each other which density decrease.
Answer:
F_n = 5.65E-11 N
d = 1.20682E-31 m
Explanation:
F = 3.8E-09 N
where
m = Mass of electron = 9.109E−31 kilograms
G = Gravitational constant = 6.67E-11 m³/kgs²
x = Distance between them

For 

Dividing the above equations we get

F_n = 5.65E-11 N

d = 1.20682E-31 m
I'm like 89% sure that the answer is C.
The photoelectric emission is possible if the wavelength of the incident light is less than that of yellow light