Consider the following statements:
1. For an isotropic medium, ε is a scalar constant.
2. For a homogeneous medium, ε, µ and σ are constant throughout the region.
3. In an anisotropic medium, D and E have the same direction.
4. For certain crystalline medium, ε varies with the direction of E.
Which of the above crystalline medium, ε varies with the direction of E.