**Explanation:**

In contract law, a contract for the sale of future goods refers to an agreement between a buyer and a seller for the purchase and sale of goods that are not yet in existence or are not yet owned by the seller at the time of the contract. The key characteristic of a contract for the sale of future goods is that the goods are to be manufactured, acquired, or produced by the seller after the contract is made.

The correct answer to the question is option 'B', an agreement to sell. Here's why:

**Sale:**
A sale refers to a contract where the ownership of goods is transferred from the seller to the buyer immediately at the time of the contract. In a sale, the goods must exist and be owned by the seller at the time of the contract. In the case of future goods, which do not yet exist or are not owned by the seller, a sale cannot occur.

**Agreement to Sell:**
An agreement to sell is a contract where the seller agrees to transfer the ownership of goods to the buyer at a future date or upon the occurrence of a specific event. In the case of future goods, an agreement to sell is the appropriate term because the goods are not yet in existence or owned by the seller.

**Void:**
Void refers to a contract that has no legal effect and is unenforceable by law. A contract for the sale of future goods is not void but rather a valid and enforceable contract, provided that the necessary elements of a contract are present.

**Hire Purchase Contract:**
A hire purchase contract is a type of agreement where the ownership of goods is initially retained by the seller (hirer) and is transferred to the buyer (hirer) upon the completion of all installment payments. This type of contract is not relevant to the question as it does not pertain specifically to the sale of future goods.

In conclusion, the correct answer is option 'B', an agreement to sell, as it accurately describes a contract for the sale of future goods where the ownership is transferred at a future date or upon the occurrence of a specific event.