Why did J.J. Thomson reason that electrons must be a part of the atoms of all elements?

Why did J.J. Thomson reason that electrons must be a part of the atoms of all elements? (1 point)

a. Cathode rays are negatively charged particles.
b. Cathode rays can be deflected by magnets.
c. An electron is 2000 times lighter than a hydrogen atom.
d. Charge-to-mass ratio of electrons was the same, regardless of the gas used.