The correct answer is B. alacrity.
Alacrity is promptness and eagerness in doing something. It is a positive quality that indicates that someone is willing and able to act quickly and efficiently.
Surmise is an educated guess or conjecture. It is a less positive quality than alacrity, as it suggests that someone is not sure of their facts and is making a guess based on limited information.
Grimaces are facial expressions that show pain, disgust, or disapproval. They are not positive qualities, as they suggest that someone is unhappy or uncomfortable.
Fear is an emotion that is characterized by a feeling of anxiety or dread. It is not a positive quality, as it suggests that someone is afraid of something.
In conclusion, the correct answer is B. alacrity. Alacrity is a positive quality that indicates that someone is willing and able to act quickly and efficiently.