What is a device invented in 1889 that plays circular, flat records?

Particle model to predict what will happen if a sharp object creates a hole in the soccer ball

Sodium nitrite (nano2) reacted with 2−iodooctane to give a mixture of two constitutionally isomeric compounds of molecular formula c8h17no2 in a combined yield of 88%. draw reasonable structures for these two isomers. click the "draw structure" button to launch the drawing utility. place the two compounds in the appropriate boxes below.

Which of the following units is not an official si unit