In a string of length L, the wavelength of the n-th harmonic of the standing wave produced in the string is given by:

The length of the string in this problem is L=3.5 m, therefore the wavelength of the 1st harmonic of the standing wave is:

The wavelength of the 2nd harmonic is:

The wavelength of the 4th harmonic is:

It is not possible to find any integer n such that
, therefore the correct options are A, B and D.
The kinetic energy of the electron is

where

is the mass of the electron and v its speed. Since we know the value of the kinetic energy,

, we can find the value of the speed v:
Work = Force * distance
Force = 70 N
Work = 3500 J
3500 = 70d
d = 3500/70 = 50 m
Answer:
leaf and a balloon is the correct answer
Relative dating is used to arrange geological events….
Relative dating puts geologic events in chronological order without requiring that a specific numerical age be assigned to each event….
Relative Dating uses the half life of isotopes to get the exact age of a rock or mineral.