________ serves as storage of liquid metal for compensating for the shrinkage during solidification of casting.

Explanation:

Pattern:​

A pattern is a replica of the object to be made by the casting process. The following points are kept in mind for pattern:

• Easily and cheaply available
• Machinable easily worked and shaped 
• Resistance to wear and abrasion.
• Non-poisonous and chemically stable.

Sprue

• A sprue feeds metal to the runner which in turn reaches the casting through gates.
• A sprue is tapered with its bigger end at the top to receive the liquid metal. The smaller end is connected to the runner.
• In many cases, it controls the flow of material into the mould. During casting or moulding, the material in the sprue will solidify and need to be removed from the finished part.

Riser:

• The riser is a reservoir of molten metal provided in the casting so that hot metal can flow back into the mould cavity when there is a reduction in the volume of metal due to solidification.
• A riser must stay in a liquid state at least as long as the casting and must be able to feed the casting during this time.

Core: 

• Cores are used to get the internal cavity in the castings.
• Cores are placed into the mould after the removal of the casting. These are made up of sand are used in permanent moulds also.
• The cores are surrounded by molten metal and therefore subjected to severe thermal and mechanical conditions.
• Core sand should be of higher strength than moulding sand.