6th Grade Reading Comprehension (2 passages, free)

Unit K-7 was the fastest delivery robot in the city. It calculated routes in milliseconds and never arrived late. Its only flaw, according to its programmers, was impatience: if a path was blocked, K-7 beeped until it was cleared.

One afternoon, K-7 rolled up to a crosswalk where an elderly man was crossing slowly with a cane. K-7’s sensors flashed red. Every second of delay lowered its efficiency score.

K-7 began to beep, then stopped. Its camera noticed the man’s grocery bag tearing at the bottom. Without being asked, K-7 extended a storage tray beneath the bag just as three oranges tumbled out.

The man laughed and thanked the robot. K-7 arrived four minutes late that day. Its efficiency score dropped, but when the programmers reviewed the footage, they added a new line to its code: “Some delays are worth it.”

Earth has about the same amount of water today as it did millions of years ago. That water keeps moving through a loop called the water cycle.

The sun heats water in oceans, lakes and rivers, turning some of it into water vapor in a process called evaporation. Plants also release water vapor through their leaves, which is called transpiration.

As the vapor rises and cools, it condenses into tiny droplets that form clouds. When the droplets join and grow heavy, they fall as precipitation: rain, snow, sleet or hail.

Some precipitation soaks into the ground as groundwater; the rest flows over land into rivers and back to the sea, where the cycle begins again.