Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions.

Music can be happy, sad, romantic, sleepy, spine-tingling, healing - all kinds of things. But what is it? Some people define it as an artful arrangement of sounds across time. Our ears interpret these sounds as loud or soft, high or low, rapid and short, or slow and smooth. The sounds need to continue for a time in some sort of pattern to become music.

Music, like language, is a uniquely human form of communication. As with language, there are many different kinds. In North America, people listen to jazz, rock, classical, folk, country, and many other kinds of music. Each kind of music has its own rules and “speaks” to us in its own way.

What we think of as music depends on where we live. What Americans are used to listening to might sound strange to someone from another culture, and vice versa. It might not even sound like music. In Indonesia, gamelan orchestras play music on gongs, drums, and xylophones. These aren't the instruments you'd find in a typical orchestra in North America.

Today, modern communications make it possible for us to listen to music from all over the world. Music from one part of the world influences music from another part. For example, gamelan music from Indonesia influenced 20th-century American composers such as John Cage.

No one knows for sure when music began. Perhaps while people were working, they began to chant or sing to make the work go faster. People who were repeating movements - picking crops or rowing boats, for example - could sing or chant in time to the work. Navajo Indians, for example, had corn-grinding songs. Many cultures developed work songs.

Over time, people developed musical instruments. They might have started by clapping their hands and stamping their feet. Sticks and objects that rattled could have replaced the human body as early instruments. Both instruments and music became more complex with time.

Today, many cultures divide music into art music and music of the people. Art music, which we call classical music, is more complicated than the music of the people - folk music and popular music. Art music is generally harder to write and perform. Musicians who perform it need a lot of training. Popular and folk styles typically are easier to create, perform, and understand.

Which of the following is given a definition in paragraph 1?

The word "crowds" in the passage mostly refers to ____.