Which of the following describes the correct criteria for when a child in Alberta can safely transition from a booster seat to using only a standard vehicle seatbelt?

1. When they are at least 4 years old and weigh 18 kg (40 lbs)
2. When they are 9 years of age, or reach a weight of 36 kg (80 lbs), or stand 145 cm (4 feet 9 inches) tall
3. When they start attending grade school
4. When their knees bend over the edge of the seat, regardless of age or height