Which helmet requirements and safety recommendations are correct? Select all correct answers.

Do not use damaged or unapproved helmets. Decorations, stickers or adhesives must not harm the shell. A full-face helmet gives extra protection. Do not buy a second-hand helmet, because damage may not be visible. This question includes legal requirements and safety recommendations: choosing a new full-face helmet is a safety recommendation, not a rule that other approved helmet types are unlawful.