Question: Easy bookshelf.

  Options: 
 A. Two planks of wood, 4 concrete bricks. Place 2 concrete bricks on the floor, as far apart as the planks are long. Place one plank resting on these 2 bricks. Place the next 2 concrete bricks on top, and place the 2nd plank on top. Voila, a sturdy easy book shelf.
 B. Two planks of wood, 4 concrete bricks. Place 2 concrete bricks on the planks, as far apart as the planks are wide. Place one plank resting on the other 2 bricks. Place the next 2 concrete planks on top, and place the 1st plank on top of the last one. Voila, a sturdy easy book shelf.
Answer: A