It's B because it talks about if it harms people. That would be an example of a medical/ethical issue.
Answer:
a.) 1.8 metre
b.) 66.67 Hz
Explanation: Given that the
Length L = 0.9m
Wavelength (λ) = 2L/n
Where n = number of harmonic
If n = 1, then
Wavelength (λ) = 2L = 2 × 0.9 = 1.8 m
b.)
If waves travel at a speed of 120m/s on this string, what is the frequency
associated with the longest wave (first harmonic)?
Given that V = 120 m/s
V = Fλ
But λ = 2L, therefore,
F = V/2L
F = 120/1.8
F = 66.67 Hz
D. F=ma
F is for force, and that equals two things, M for mass and A for acceleration. When mass is accelerated, it gives you force. Force equals multiplying mass and its acceleration.
Compression and rarefraction, the other guy's answer it's wrong
Explanation:
It is given that,
Voltage, 
De broglie wavelength in terms of voltage is given by :
m and e are the mass and charge on electron. So,
So, the De broglie wavelength of an electron is 1.53 meters. Hence, this is the required solution.
