Why is it unwise to pass near the top of a hill on a two-lane highway?

• Because you won’t be able to see what is ahead of you.
  Explanation:

  "Passing near the top of a hill on a two-lane highway is dangerous because your visibility of oncoming traffic is limited. Without a clear view of the road ahead, you risk a head-on collision. Always wait until you have full visibility before attempting to pass."
• Because you might suddenly reach the top of the hill and start descending.
• Because the cars behind you might start following you.
• None of the above.