The sentence that is correctly written is C. Dr. Thomas played the role of a brain surgeon in the TV series General Hospital.
This is the correct option because there must be a period after the abbreviation Dr. (which stands for 'Doctor'). Sentence A) does not include the period; therefore, it is incorrect. Moreover, the initial letters in the words 'General Hospital', that is 'G' and 'H', must be capitalized because it refers to the name of a TV show. Sentence B) does not capitalize these letters; therefore, it is incorrect. Sentence C) is the correct option.