Going Green

Today Isabel says to me, "When you have gas, it makes the planet kind of stinky."
Me: "Ummmmm..."
Isabel: "Mommy, when we have gas it makes the planet stinky."
Me: "Well, I guess that's true..."
Isabel: "We read a book called Going Green at school today and it said that when you have gas it makes the planet stinky. So that's why you should walk sometimes."
Me: ...blink...blink...blink...
Me: "OH! You mean when we USE gas. Yes, we should drive less and walk more, sweetie."