Here are some words to help answer the question "Which one?" We distinguish between singular and plural as well as between something close to us and far away.

We learn more about how water interacts with the minerals in the rocks, and visit Monument Valley, a popular spot for filming westerns and commercials.

In this segment, we learn about the role weather plays in the creation of rock formations in the national parks of the United States.

Watch some coverage of the People's Climate March that was timed to coincide with the UN Climate Summit in New York City. The march was attended by 400,000 people.

Geysers represent a very popular tourist attraction in Yellowstone Park. How do they work and where do they come from? And what is sandstone? The video answers these questions.

Lindsey Vonn describes her early days on the slopes, the encouragement she received from her father, and coming back from the many injuries she has endured on her way to becoming a champion skier. She also talks about her decision to compete against men in alpine skiing.

In Yellowstone Park, visitors can see many indigenous animals in their natural habitat and wonder at the park's natural hot springs.

Natalie Fee concludes her Ted Talk with a few suggestions for what we can do to reduce how much single-use plastic we are sending into the earth's waterways.

"One" and "ones" can replace nouns, but are not pronouns. They are prop words. Let's look at how they are used.

Why are some rock formations and animals found on more than one continent? The explanation dates back to the Ice Age.

The birth cycle of kangaroos, affectionately called “roos,” is the subject of this video from National Geographic.

Why do some of the national parks in the United States resemble the European Alps? Geologist Dr. Robert Darga answers this question.

Natalie provides some tips for wasting less plastic and leaves us with a slogan to help us rethink our flushing habits. She involves the audience to bring the message home.

Here's the trailer for an inspiring film about the efforts of ordinary people to make the world a more sustainable place. Experts talk about the necessity of taking action.

Go behind the scenes of Entertainment Weekly's cover shoot with Dwayne Johnson as he gets into the holiday spirit! He has fun playing “Dwanta Claus,” lists his favorite holiday movie and song, and talks about his appreciation of the gifts he receives from fans.