Balance the following and label what type of reaction is taking place:   c5h9o + o2? co2 + h2o

The given reaction is C₅H₉O + O₂ → CO₂ + H₂O

On balancing the equation we get:  

20 C₅H₉O + 90 O₂ → 100 CO₂ + 9 H₂O

This is a single replacement type of reaction. A single replacement reaction, also called a single-displacement reaction, refers to a kind of chemical reaction where an element reacts with a compound and occupies the place of another element in that compound.  

it is the most commonly accepted one