Complete the sentence with the best choice in spanish. at the beginning of each lesson is the  explicación. introducción. escribir. escuchar. apuntes. vocabulario. investigar. en clase. presionar. practicar.

I guess it's refering to the "introducción", which means the "introduction", but maybe it refers to the beginning of the actual lesson and not the class, so it could be "explicación", which means "explanation".