Please help me with the real answer How can we use the part interactive simulation to model buiding simple molecules​??​

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)

a- multicellular

b-eukaryotic

c-no cell wall

d-heterotrophic

e-autotrophic