What is the most appropiate unit of measurement fro most types of cells?

Solution:

The most appropiate unit of measurement fro most types of cells is CD4 counts are measured in cells per cubic millimetre = cells/mm3. A cubic millimetre (mm3) = mm3 = 1 mm x 1 mm x 1 mm.

This is the required answer.

it is a limiting nutrient limited by a single nutrient in the ecosystem, & the single goes very slow.