Какое слово нужно поставить на месте пропуска и почему? The --- is all the goods a retail outlet keeps to sell to its

The stock is all the goods a retail outlet keeps to sell to its customers.

The stock is a supply or quantity of something accumulated or available for future use.

A checkout counter is a place where you pay for your goods.

Is the stock all the goods a retail outlet keeps to sell to its customers?

What is all the goods a retail outlet keeps to sell to its customers?

The stock is all the goods a retail outlet keeps to sell to its customers, is not it?