The intensive property of a rectangular block of wood is density. So the student should determine the density to examine the intensive property.
Answer: D
Explanation
The intensive properties of a substance are the physical properties which does not depend on shape and size of the substance.
The extensive properties will depend on the shape and size of the substance.
Among the options given, the mass of the wooden block will depend on the size of the block, so it will be an extensive property.
Similarly, the length and volume will also vary with the size of the block, so they also fall on extensive property category.
But the density of the wooden block will be ratio of mass with volume, so the density will not vary with the size.
The density will be constant, so it an intensive property.