English Translation
When the teacher asked who wanted to participate, María was the first to raise her hand.
There seem to be some contradictory definitions of alzar el dedo. The RAE has this definition:
loc. verb. Levantar un dedo o la mano para pedir la palabra o mostrar acuerdo con lo que se propone.
Disturbingly, Wiktionary says the following:
(idiomatic) to give the finger (make an obscene gesture)
Perhaps it’s safer to just say “alzar la mano”?