The reaction given is:
4Ga + P4 ---> 4GaP
The oxidation number of the reactants is zero, because they are pure elements.
The P in compounds may have oxidation states 3- or 5-. Gallium may only have oxidation state 3+.
Then, to be neutral in GaP the oxidation states are 3+ for Ga and 3- for P.
And the transference of electrons can be see in this oxidation - reduction equations:
Ga (0) - 3 e- ----> Ga (3+)
P (0) + 3e- ---> P (3-)
So, for one formula unit, 3 electrons have been transfered from each Ga atom to P atom to form one GaP unit.
Answer: 3 electrons.
<h2>Answer:</h2>
Compound. Option A is correct
<h2>Explanations:</h2>
When two or more different elements combines, a compound is formed. For instance, if carbon and oxygen combines, carbondioxide is formed according to the equation;

From the reaction, carbon and oxygen are the elements while carbondioxide is the compound. Hence we can conclude that a pure substance formed when two or more different elements combine called compound.
It is clean and is blue when you take away air hope i helped.