Concept:
A contract of sale involves the transfer of ownership of goods from seller to buyer for a price.
Step 1: Essential elements.
- Two parties $\rightarrow$ Buyer and seller
- Transfer of property $\rightarrow$ Ownership of goods must be transferred
- Price $\rightarrow$ Consideration must be in monetary terms
Step 2: Evaluate options.
Each of the given options represents an essential element of a contract of sale.
Step 3: Conclusion.
Thus, all of the above are essential elements.