The unit of measurement that scientists use to determine the diameter of an animal cell is the

Meter, inch, mile, yard, Astronomical Unit, lightyear, parsec, planck length, sheppey.

We can use all of these and many more to determine the diameter of a cell. We can use them all easily because of scientific notation.

Take your pick! You teacher cannot mark you wrong as long as it's a unit of length. (Sheppey might be stretching it a little too far!).