Explanation

The blank must describe the doctor’s friends, so look for the clue that gives information about those friends. The friends quickly jilted him, meaning that they dishonorably abandoned him.

Friends who would do that are not very good friends, so you’re looking for a word that means not loyal. Squeamish describes someone who becomes uncomfortable easily, usually around things that are unpleasant to the senses (blood, rodents, etc.). While the friends may be uncomfortable in the doctor’s presence, that’s not why they abandoned him. Orthodox and stodgy describe people who adhere rigidly to convention. These words describe the medical establishment, not the friends. A staunch ally is one who is loyal, so that word means the opposite of the blank. Fickle and inconstant both mean disloyal, and so they are good fits for the blank.

Hence options B and D are correct.