Question

Since 1900, music became...

...non-existent, because all music and instruments were destroyed during wars.

...strongly unified, organized, and standardized: all composers followed the same formal and tonal models.

...very individualized: one composer, or small groups of them, developed their own style(s).

...entirely improvised: no music was ever written down anymore.

Answer 1

…very individualized: one composer, or small groups of them, developed their own style(s)

Today there is a nearly endless number of music styles. There is no standard formal model, and people still write the music down. And for sure music still exists.