I Wonder Why - Be Amazed! 20-Book Set

I Wonder Why Series 20 Books Collection Set:

Titles In This Set:
Zips Have Teeth
The Wind Blows
Triceratops Had Horns
The Sun Rises
Spiders Spin Webs
Soap Makes Bubbles
The Sea is Salty
Romans Wore Togas
Pyramids Were Built
Planes Have Wings
Stars Twinkle
Castles Had Moats
Caterpillars Eat So Much
Countries Fly Flags
Hurricanes Have Eyes
I Sleep
Kangaroos Have Pouches
Leaves Change Colour
Penguins Can't Fly
Pirates Wore Earrings.