Answer:
Synthesis reaction
Step-by-step explanation:
To know which option is correct, it important that we know what each option represents.
Synthesis reaction is a reaction in which two different elements react to form a single compound. For example
X + Y —> XY
Decomposition reaction is a reaction in which a compound splits into two or more simpler substance. For example
XY —> X + Y
Single Replacement reaction is a reaction in which one element replaces or displaces another element from a compound. For example
X + YZ —> XZ + Y
Double Replacement reaction is a reaction in which the parts of two ionic compounds exchange their ions to form a new compound. For example
WX + YZ —> WZ + YX
Now, considering the equation given above i.e
P + O₂ —> P₄O₁₀
We can see that P and O₂ reacted to produce a new compound (i.e P₄O₁₀).
Thus, the reaction is a synthesis reaction because two different elements (i.e P and O₂) reacted to form a single compound (i.e P₄O₁₀).