It is illegal to leave a child age six or younger unattended in a vehicle on a hot day:

  1. Even if they are secured in a child passenger restraint system. ✓
  2. If they are supervised by a person twelve years of age or older.
  3. Only if the key is in the ignition.

Answer: A. Even if they are secured in a child passenger restraint system.

Yes. It is illegal to leave a child age six or younger unattended in a vehicle on a hot day even if they are secured in a child passenger restraint system.

Why this is the answer

The handbook says leaving a child who is six years old or younger unattended in a vehicle is illegal. It allows the child to be left only under the supervision of a person who is at least 12 years old. A child passenger restraint system holds the child in place, but it does not supervise them. The same passage calls leaving children in a hot vehicle dangerous and illegal, and says the inside temperature can rise quickly even if a window is slightly open.

Why the other answers are wrong

Remember it

A safety seat is not a babysitter; someone at least 12 must be watching the child.

Official handbook: California Driver Handbook (DL 600), Section 8: Safe Driving, p. 67

Explanation drafted with AI (deepseek-flash) from the official handbook passage cited above, then checked automatically and by a second model on 2026-10-23. Always confirm with the official handbook.