Answer:
The correct answer is option b. "He passed cathode rays through a magnetic field and measured the deflection".
Explanation:
J. J. Thomson was a notorious scientist that did not only made the discovery of the electron, but he measure its charge to mass ratio. In order to determine this property, Thomson passed cathode rays through a magnetic field and measured the deflection. Cathode rays are actually composed of particles, which are now known as electrons, and its charge to mass ratio is about 10^8 coulomb per gram.
That's a ketone's functional group :)
