Why is it unsafe to drive behind a log hauling truck when it is turning left or right?

• When these trucks are turning, the logs can block all or some of the lanes of the highway.
  Explanation:

  "Never pass a log hauling truck that is turning left or right off the highway. When these trucks are turning, the logs can block all or some of the lanes of the highway."
• When these trucks are turning, the logs can fall off and hurt someone.
• When these trucks are turning, nothing happens.
• None of the above.