Which act would NOT constitute theft under Texas law?

Taking a friend's item with their permission does not constitute theft under Texas law because theft is defined as unlawfully appropriating property with the intention to deprive the owner of it. In this scenario, since permission was granted, there is no unlawful taking involved, and therefore no theft has occurred.

In contrast, the other options describe actions that directly align with the definition of theft. Unlawfully obtaining control over someone else's property clearly involves a lack of consent, and exerting control over property with the intent to deprive the owner indicates a deliberate act of theft. Additionally, attempting to take property without consent also falls within the realm of theft since there is no authorization from the owner for such an action. Hence, only the act of taking an item with permission is excluded from constituting theft.