Blow moulding involves...

• A. A tube of molten plastic is extruded between two halves of a mould, air is blown into the molten plastic to make the shape of the product
• B. A mould is created from wood or epoxy resin
• C. A sheet of plastic is heated until it becomes soft and placed over the mould
• D. A screw thread turns forcing the plastic into the mould where it cools

Answer: (A)

Blow moulding forms hollow shapes by inflating a hot tube of plastic inside a mould. A parison or tube is extruded between two halves of a mould, and then air is blown into it so the plastic expands to press against the cavity walls. The mould is cooled and opened to release the hollow product, like bottles or drums.

This matches the described process where a tube of molten plastic is extruded between mould halves and air is blown in to shape the product. The other options describe different methods: using a sheet of plastic heated over a mould is thermoforming; forcing melted plastic into a mould with a screw is injection moulding; and mould materials reference how the mould itself is made rather than how the part is formed.