WILL GIVE BRAINLIEST AND 15 POINTS IF YOU ARE CORRECT!!!

Read the paragraph below. Select the underlined group of words that is a clause functioning as an adverb.

Soccer (or football, as it is called in most of the world) has been extremely popular in many countries for at least a century. In the United States it has gained popularity more slowly because other sports are so established.

These are the options from that sentence.

A. In most of the world.

B. Has been extremely popular in many countries for at least a century.

C. In the United States it has gained popularity.

D. Because other sports are so established.