Identify the concept

The question refers to conversion of a temperature difference into electrical energy. This is the thermoelectric effect (Seebeck effect).

Requirement for a good thermoelectric material

A good thermoelectric material should:

• allow charge carriers to move easily $\Rightarrow$ high electrical conductivity
• prevent heat from flowing quickly from hot end to cold end, so that the temperature difference is maintained $\Rightarrow$ low thermal conductivity

Reasoning

If thermal conductivity is high, heat will quickly flow through the material and reduce the temperature gradient, which decreases thermoelectric generation.

If electrical conductivity is low, the generated charges cannot flow efficiently, so electrical output is poor.

Evaluate the options

• A: low thermal conductivity and high electrical conductivity $\rightarrow$ correct
• B: low thermal conductivity and low electrical conductivity $\rightarrow$ poor electrical transport
• C: high thermal conductivity and high electrical conductivity $\rightarrow$ temperature gradient not maintained
• D: high thermal conductivity and low electrical conductivity $\rightarrow$ worst combination

Final answer

The required property is: $\boxed{\text{low thermal conductivity and high electrical conductivity}}$ So, the correct option is A.