What Sound Does a Zebra Make?

I've compiled a few questions the kids have asked me about recently that I've been promising to research for them.

Asher: "What sound does a zebra make?" I guessed that it might sound like horse's neigh, while Asher suggested that it made no sound at all. Answer: A cross between a donkey's bray and a small dog's bark.

Elliot: "How old is the world's oldest living person?" Answer: According to wikipedia, the oldest person is 115 year old Edna Parker of the United States. There is a Japanese man who is 120, but his age is not confirmed. The previous oldest living person record holder was Jeanne Calment, who died at age 122 and 164 days.

Elliot: "What makes storm clouds dark and white clouds white?" I looked up the answer on wikipedia, but the answer was a little too scientific for me. Here are the answers compiled from a few sources:

White clouds are white because: Clouds are illuminated by light from the sun, and light from the sun is seen as white by our eyes, a mix of all the colors of the rainbow - which produces white. Clouds are made up of many small water drops and ice crystals. Light reflects and scatters so many ways from and in a cloud that when illuminated directly it ends up looking bright white.

Dark clouds are dark because: Clouds can also look dark or gray due to perception by our eyes. A light gray cloud on a bright white background will look much darker than the same cloud on a dark or black background, in which case it might look white and bright. A cloud can also look dark or gray because it is partially transparent and the blue sky behind it can be seen through the cloud.