4

How they Work? Trains

4

Niagara Falls

4

Okavango Delta, Botswana

3

Neil Armstrong

4

Mount Fuji, Japan

3

Motion

2

Lake Day

4

Felix's Independence Day

3

Police Officer

3

Space Exploration

3

Firefighter

3

Pollution

3

Astronauts

3

Meteorites, Meteoroids, and Meteors

3

Bus Driver

4

Hoover Dam

4

Maddy's New Hampshire Diary

4

Victoria Falls, Zimbabwe/Zambia

4

Gorillas and Other Primates

3

Comets

2

Who Works Here?