Which one of the following items is not a standard rated VAT supply?

The question asks which item is not a standard-rated VAT supply. This refers to items where the VAT treatment differs from the standard rate, particularly concerning the ability to claim input VAT.

• a. Trading inventory: Goods purchased for resale are typically subject to standard-rated VAT, and businesses can claim input VAT on their purchase.
• b. Stationery: Office supplies like stationery are generally subject to standard-rated VAT, and businesses can claim input VAT.
• c. Passenger vehicle: In many VAT systems (e.g., South Africa), businesses are generally not allowed to claim input VAT on the purchase of passenger vehicles, even if used for business, unless the business's main activity is dealing in or hiring out such vehicles. This makes them effectively not a standard-rated VAT supply for input VAT purposes for most businesses.
• d. Office equipment: Items like computers, printers, and furniture are typically subject to standard-rated VAT, and businesses can claim input VAT on their purchase.

Therefore, a passenger vehicle is the item that is generally not treated as a standard-rated VAT supply for input tax purposes for most businesses.

The correct option is c.

$\boxed{\text{c. Passenger vehicle}}$