The Lewis structure depicts the number valence electrons surrounding an atom. These are the electrons present in the outer shells which can participate in bonding with another atom or remain as non-bonding (lone pair) electrons.
In the given example there are 7 dots or 7 electrons surrounding a Cl atom. This corresponds to 7 valence electrons with a configuration that can be given as: s²p⁵ and specifically, 2s²2p⁵
Dalton is 1st, he made the atomic theory.
JJ Thomson is 2nd, he made the plum pudding model of the atom.
Earnest Rutherford is 3rd, he disproved the plum pudding model with alpha particles being shot at gold.
Bohr is 4th, he also made another model after Rutherford
C is your answer. This is simple chemistry history, your teacher should have taught you this