Which one of the following is not an example of a compressional wave?

a) wave moving through a coiled spring
b) sound traveling through the air
c) sound traveling through water
d) green light traveling through the air

I think the answer is (D) green light traveling through the air, but i'm not 100% sure

Grilled ham and cheese sandwich: caution: if you’re underaged then have a responsible adult supervising you to prevent any injuries.1. preheat a pan or griddle over medium heat. spread each bread slice with mustard — crust to crust is a must to get full coverage so that each bite is identical. if you don’t like mustard then use whatever else you like.2. use a trio of cheeses in a grilled cheese to achieve perfect harmony: 1 slice of american cheese for gooeyness, 1 slice of aged cheddar for sharpness and 1 slice of provolone or mozzarella for stringiness. if you don’t like these cheeses then use whatever else you like.3. ribbon your meat onto your sandwich to create dramatic height and a smoother bite down. don't just lay the meat flat — it makes for a flat sandwich.4. add anything else you'd like to the sandwich — (just make sure you season them with a bit of salt and 5. spread mayo on the outside of a grilled cheese before it goes into the pan or onto the griddle, which ensures that it will be perfectly golden brown every time.6. place on the griddle; dome your grilled cheese with a metal bowl to create a vortex of heat and ensure the cheese melts without over-toasting the exterior for a maximum of 3 minutes. flip, cover again and cook until the cheese is melted and the sandwiches are golden brown for a maximum of 3 minutes. hope this : )