Fe + Cl2  Fe FeCl3 2. Al + O2 Al2O3
3. Fe3O4 + H2 Fe + H2O
4. P2O5 + H2O  H3PO4
5. Al(OH)3  Al2O3 + H2O
6.Ba(OH)2 + HCl  BaCl2 + H2O
7. Zn + Fe(NO3)3 Zn(NO3)2 + Fe
8. C3H6 + O2  CO2 + H2O
9.Ba(OH)2 + AlCl3  Al(OH)3 + BaCl2
10.Mg + Al2(SO4)3 MgSO4+ Al

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.

answer: they produce more slow than unicellular organisms.

catya that's not even a b or c