Explanation:

- Option 1: J.J. Thomson

- Discovered the electron through experiments with cathode rays in 1897.

- Known for the plum pudding model of the atom.

- Option 2: E. Goldstein

- Credited with discovering canal rays, which are streams of positively charged particles.

- His work contributed to the identification of the proton but did not discover it directly.

- Option 3: E. Rutherford

- ?? Discovered the proton through his gold foil experiment in 1911.

- Proposed the nuclear model of the atom with a central positive charge.

- Option 4: J. Chadwick

- Discovered the neutron in 1932.

- His discovery helped explain isotopes.

. The correct answer is Option 3: E. Rutherford.