what coefficients would balance the following equation?

__al + __o2 → __al2o3
question 4 options:

(a) 2al + 3o2 → 1al2o3

(b) 2al + 3o2 → 2al2o3

(c) 3al + 3o2 → 2al2o3

(d) 4al + 3o2 → 2al2o3

The answer to your question is: Letter D.

Explanation:

To have a balanced reaction, the number of elements in the reactants, must be equal to the number of elements in the products.

So, count the number of elements in each side.

                                                __Al + __O2 → __Al2O3

                      reactants                elements         products

                            1                              Al                      2

                            2                             O2                     3

It's unbalanced

Write a coefficient 4 in Al       4 Al +   3O2 →   2Al2O3

                               3 in O2

                              2 in Al2O3

And count again the number of elements

                        reactants                elements         products

                              4                              Al                      4

                              6                             O2                     6

Now, the reaction is balanced

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

while cooking a piece of 1/2 pound beef steak, a cast iron pan (2.4kg in weight) was heated 260 celsius.