Recall what a semiconductor is

A semiconductor is a substance whose electrical conductivity lies between that of a conductor and an insulator. Common examples include:

• Silicon ($\mathrm{Si}$)
• Germanium ($\mathrm{Ge}$)
• Some metal oxides like copper oxide

Check each option

A. Copper oxide

• Copper oxide is generally treated as a semiconductor material.
• So, this is not the correct choice.

B. Graphite

• Graphite conducts electricity due to the presence of delocalized electrons between its layers.
• It behaves as a conductor, not a semiconductor.
• So, this is a strong candidate for the correct answer.

C. Silicon

• Silicon is a classic semiconductor.
• So, this is not the correct choice.

D. Germanium

• Germanium is also a classic semiconductor.
• So, this is not the correct choice.

Conclusion

The material which is not a semiconductor is: $\boxed{\text{Graphite}}$

Comparison with stored correct answer

• Derived answer: B
• Stored correct answer: B

Hence, the derived answer agrees with the stored correct answer.