Question

choose the word or phrase that best defines the italicized word Triumphantly pressing down the alarm-knob of the clock which the dark half of his mind had outwitted remaining vigilant all night

Answer 1

Triumphantly is an adverb, so you would be looking for the verb that it modifies. I would choose the word “pressing.” Ask yourself, “how did he press down the alarm knob?” He pressed it triumphantly.