Final answer:
The Texas Real Estate License Act requires a license holder to be a practicing attorney when advising a person on the validity of title to real property. Other tasks mentioned do not require attorney status.
Step-by-step explanation:
According to the Texas Real Estate License Act, the activity that requires a license holder to be a practicing attorney is advising a person regarding the validity of title to real property. The other options, such as filling in a TREC-promulgated contract, advising a client to reject an offer, or determining the offering price for a seller, do not specifically require the license holder to be a practicing attorney. These tasks are within the scope of responsibilities typically handled by real estate professionals who are not attorneys.