Is there an error in this code? If so, find the best description of the problem

@font-face {
  font-family: 'Avenir', sans-serif;
  src: url('avenir.woff2') format('woff2'), url('avenir.woff') format('woff');
}

1.  The font file formats are not supported in modern browsers.
2.  The src attribute requires a comma between the URL and format values.
3.  There are no errors in the example.
4.  The sans-serif inclusion is problematic.

Correct Answer:

•  The sans-serif inclusion is problematic.