Final answer:
Bus passengers are most commonly injured when the driver stops or starts too quickly. This rapid change can cause passengers to fall if they're not secured. Cars with crumple zones increase the time of impact in a collision, improving passenger safety.
Step-by-step explanation:
When passengers on a bus are injured, it is typically due to sudden starts or stops by the driver. The correct answer to the student's schoolwork question is option b, 'The driver stops or starts too quickly.' Quick actions by the bus driver can lead to rapid acceleration or deceleration, which may cause passengers to lose balance and get injured if they're not seated or holding onto something securely.
The issue of safety in vehicles related to sudden movement can also be seen in the design of modern cars. The correct answer to the question on cars having parts that can crumple or collapse in the event of an accident is option a: 'It reduces injury to the passengers by increasing the time of impact.' Crumple zones are engineered to absorb impact energy during a collision, which reduces the force transferred to the passengers and thus lowers the risk of injury.