Correct option is C
High Tricalcium Aluminate (C₃A): Correct. It is the primary cause of flash set in cement.
High Alkali Content: Correct. Alkalis enhance the reactivity of C₃A and contribute to quick setting.
High Tricalcium Silicate (C₃S): Incorrect. Although C₃S contributes to initial strength development, it is not a significant cause of flash set.