Questions: What should you say when a classmate lends you a book? Gracias. What should you say when you accidentally step on someone? Gracias. What should you say when you need to pass through a group of people? Con permiso. What should you say when you need to get your professor's attention? Por favor. What should you say when you need to get the attention of someone on the street? Perdón.

The answer is "Lo siento."

"Gracias" is used to express gratitude, such as when a classmate lends you a book.

"Lo siento" is the appropriate response when you accidentally step on someone, as it means "I'm sorry."

"Con permiso" is used when you need to pass through a group, as it politely asks for permission to pass.

"Por favor" is used to politely request something, such as getting your professor's attention.

"Perdón" is used to get the attention of someone on the street, as it means "excuse me" or "pardon."