Agreement to Sell:
An agreement to sell is a contract in which the seller agrees to sell the goods to the buyer at a future date, subject to certain conditions. Until the conditions are fulfilled, the property in the goods remains with the seller. The buyer acquires an equitable interest in the goods, but the legal ownership does not pass to the buyer.

Property Passing on Full Payment and Execution of Sale Deed:
In the given scenario, the contract states that the property will pass to the buyer on full payment of the price and execution of a sale deed. This means that once the buyer has paid the full price and the sale deed has been executed, the legal ownership of the goods will be transferred from the seller to the buyer.

Explanation of the Correct Answer:
The correct answer is option 'B' - agreement to sell. This is because an agreement to sell is a contract where the property in the goods remains with the seller until the conditions mentioned in the contract are fulfilled. In this case, the condition is full payment of the price and execution of a sale deed. Once these conditions are met, the property will pass to the buyer.

Other Options:
Let's take a look at the other options and understand why they are not the correct answers:

- Option 'A' - Sale: This option implies that the sale has already taken place and the property has passed to the buyer. However, in the given scenario, the property will pass to the buyer only on full payment of the price and execution of the sale deed. Therefore, option 'A' is not the correct answer.

- Option 'C' - Hire-purchase agreement: A hire-purchase agreement is a type of agreement where the goods are initially hired by the buyer and ownership is transferred to the buyer upon completion of all installment payments. However, in the given scenario, the contract does not mention any installment payments or hire-purchase arrangement. Therefore, option 'C' is not the correct answer.

- Option 'D' - Sale of approval: Sale of approval refers to a contract where the buyer has the option to approve or reject the goods after inspection. However, in the given scenario, there is no mention of approval or rejection of the goods. Therefore, option 'D' is not the correct answer.

In conclusion, the correct answer is option 'B' - agreement to sell because the contract states that the property will pass to the buyer on full payment of the price and execution of a sale deed.