What are the warning signs that can tell if you are at risk of becoming drowsy?

• You are having trouble keeping your head up.
• You are drifting from your lane, following too closely, or hitting a shoulder rumble strip.
• You are feeling restless and irritable.
• All of the above
  Explanation:

  "The following warning signs indicate that you are at risk of becoming drowsy: 1. Trouble keeping your head up. 2. Drifting from your lane, following too closely, or hitting a shoulder rumble strip. 3. Feeling restless and irritable."