Which sentence should be part of the technical description of a billiard ball?

1. A billiard ball is designated as a cue ball when it is used to strike the other balls on the table.
2. A billiard ball made of celluloid is often substituted for the older billiard ball made of ivory.
3. A billiard ball is spherical in shape , weighs about 6 ounces , and has a diameter of 2.25 inches.
4. A billiard ball with stripes and numbers was introduced into the game in the early 1770s.