Which of the following is an example of time utility?

a$.$ A car manufacturing company could sell all the parts of their cars separately. However, by assembling the parts $($and manufacturing cars$),$ this company adds significant value for their customers.

b$.$ This utility can be created whenever a client is handed the keys to their new car, simply because from that moment they are free to do whatever they want to do with it$.$

c$.$ If a car manufacturer sells exclusively within the US$,$ buying a car is not very attractive for Europeans. However, if the company decides to open dealerships across Europe and sell cars overseas, the availability of its cars for European customers increases.

d$.$ Customers often have to wait several weeks or even months for a new car. However, many of them need their vehicles as soon as possible. Thus, if the manufacturer manages to reduce delivery times by even just a few days, its cars become more attractive to potential customers.