Under what condition is smoking permitted on a school bus?

Smoking is permitted on a school bus under the condition that no pupil is aboard. This policy is in place to protect children from exposure to harmful substances, as schools prioritize the health and safety of their students. When there are no pupils present, the typical restrictions regarding smoking can be relaxed since the primary concern of providing a safe environment for children is mitigated.

The other conditions presented do not align with the existing regulations that protect students. For example, allowing smoking in the presence of adults or upon request by a parent does not prioritize the health of children. Additionally, stating that smoking is never permitted overlooks the specific scenarios where regulations may allow for it when pupils are absent, making the correct answer significant in understanding school bus regulations concerning student safety.