I believe the answer is D
The nervous system thin fibers are the nerves
6. f = 128.62
, T= 0.0077775 s
7. f = 2.2 *
, T = 4.545 *
s
8. 32.64 
9. 3.29 *

Explanation:
Step 1:
6.
For light and sound v = fλ
where v represents the velocity
f represents the frequency
λ represents the wavelength
λ = 2.69 m
v = 346 m/s
f = v/λ = 346/2.69 = 128.62 
Time period is the reciprocal of frequency
T = 1/128.62 = 0.0077775 s
Step 2:
7.
λ = 110 cm = 1.1 m
v = 2.42*
m/s
f = 2.42*
/1.1 = 2.2 *

T = 1/(2.2*
) = 4.545 *
s
Step 3:
8.
λ = 10.6 m
v = 346 m/s
f = v/λ = 346/10.6 = 32.64 
Step 4:
9.
λ = 5.89 *
m
v = 1.94 *
m/s
f = v/λ = 3.29 *

Answer:
Mass of the box is 3.06 kg
Explanation:
Potential energy (that depends on gravity) is the type of energy which is stored that relies on the general position of different parts of a body. It is a property of a framework and not of an individual body or molecule; the framework made out of the Earth and the raised ball.
P.E = m.g.h Equation(1)
as we have to find the mass of the box then the formula for the mass will become
m=P.E/g(h) Equation(2)
as we know
P.E= 120J
h=4m
g=9.8m/s
g is the gravitational acceleration
putting values in the equation(2)
m = 120/9.8(4)
= 120/39.2
= 3.06 kg
mass of the box is 3.06 kg