Why should you be careful when following a bus or truck approaching a railroad crossing?

• Because they may suddenly stop to let passengers off
• Because they may suddenly speed up to beat the crossing gates
• Because most buses and some trucks must stop at railroad crossings
  Explanation:

  "If you are following a bus or truck approaching a railroad crossing, be careful. Most buses and some trucks must stop at railroad crossings."
• Because they may unexpectedly turn at the crossing