33. When Does Lightning Strike?

When there’s a storm, you can measure how far away

it is by counting the number of seconds between the flash of lightning

that streaks across the sky and the sound of rumbling thunder.

Sound travels about one thousand feet in one second (33)______.

You should multiply one thousand by the number of seconds you counted and you can determine (34)______.

Lightning used to terrify prehistoric people because they didn’t know how to protect themselves from it.

But by setting trees on fire it gave them fire long before they had discovered (35)______.

The people of ancient times used to believe that lightning was a sign of the gods’ anger sent to earth (36)______.

Humans later learned to protect themselves from these electric bolts from the sky (37)______.