Identify the materials

• Copper is a metal.
• Germanium is a semiconductor.

Effect of lowering temperature on a metal (copper)

• In metals, resistance is mainly due to collisions of electrons with lattice vibrations.
• When temperature decreases, lattice vibrations decrease.
• Hence electron scattering decreases, so resistance decreases.

Therefore, for copper: $R_{\text{copper}} \downarrow$

Effect of lowering temperature on a semiconductor (germanium)

• In semiconductors, conduction depends strongly on the number of charge carriers.
• As temperature decreases, fewer electrons get enough thermal energy to move into the conduction band.
• So the number of charge carriers decreases sharply.
• Hence resistance increases.

Therefore, for germanium: $R_{\text{germanium}} \uparrow$

Match with the options

• A: copper increases and germanium decreases ❌
• B: each decreases ❌
• C: each increases ❌
• D: copper decreases and germanium increases ✅

Final answer The correct option is: $\boxed{\text{D}}$