The answer is D) combustibility.
Now I'll explain why.
Density is about mass within a volume. Both mass and volume are physical properties, not chemical.
Boiling point is the temperature when a substance start to boil. Boiling is also a physical property, chemical change isn't supposed.
Malleability is the extent to which a substance may change its form without breaking. Changing form is also a physical property.
In contrast, combustibility speaks about the ability of making compound with oxygen. This is a chemical phenomenon, it involves changes of molecules' composition.