We cannot see evaporation because water vapor is invisible. how can we tell it is happening?

pressure or try an experiment

Explanation:

Water vapor imagery is created using a wavelength sensitive to the moisture content in the atmosphere. In this imagery, bright blue and white areas indicate the presence of high water vapor or moisture content, whereas dark orange and brown areas indicate little or no moisture present.

nucleus

would be most reasonable answer tbh

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.