Why chemists use masses in grams instea
of amu.

it is a unit of mass used to express atomic masses and molecular masses. when the mass is expressed in amu, it roughly reflects the sum of the number of protons and neutrons in the atomic nucleus (electrons have so much less mass that they are assumed to have a negligible effect)

because growing process had stoped after 4-5 year

the awnser is d you right bro