Which One of the Following Is Most Likely a Sunk

Which one of the following is most likely a sunk cost?

A) the money you spent last week fixing your car's transmission
B) the market value of an idle machine which you have decided to use for a new project
C) the cost of a worker to operate an idle machine which you have decided to use for a new project
D) the cost of the health insurance which you must pay a worker that you plan to hire for a new project
E) the reduction in sales of an existing product caused by the introduction of a new product