A valid contract for the sale of real estate MUST include:

An acknowledgment is not a required element of a real estate contract. It refers to the formal recognition of a signature or agreement but does not itself constitute part of the contract's essential elements. Therefore, while it may be useful for certain legal purposes, it is not a necessity for the validity of the contract.

While a seller's deed may be relevant in the transfer of property ownership, it is not a mandatory requirement for the formation of a valid contract. The contract must focus on the agreement between the buyer and seller, rather than the documentation of ownership, making this choice incorrect.

The signature of a witness is not universally required for the validity of a real estate contract. Many jurisdictions allow contracts to be valid without witness signatures, provided the essential elements of offer and acceptance are present. Thus, this choice does not reflect a necessary component of a valid real estate contract.