Choose all the correct answers.
Which relative clauses are defining, giving us essential information about someone or something? Do they have commas?

• She invented a torch which is powered by the heat of your hand.
• Makosinki, who was born in Canada, invented the device for a friend.
• This is something which other generations find difficult.
• She had a friend who failed her exams because she had no electricity.
• The agency, which is based in New York, has been investigating Gen Z.
• Touch screens, which teenagers use all the time, may be responsible for students gradually losing the ability to write.
• Yes, they have commas.
• No, they don't have commas.