Final answer:
The liner must be either non-metallic or non-ferrous metal.
Step-by-step explanation:
The subject of this question is Physics.
The statement refers to a liner that must be either non-metallic or non-ferrous metal.
To understand this statement, it is important to know that metals can be broadly classified into two categories: ferrous and non-ferrous. Ferrous metals contain iron, while non-ferrous metals do not.
Therefore, the liner mentioned in the statement should be made of a material that either does not contain any metal or contains a metal that is not ferrous.