Why is a currency put or call not profitable to exercise when it is "at the money"?

Select one:

a.

because the spot equals the price but the premium is not recovered if it is exercised resulting in a loss

b.

When an option is "at the money," the Exchange will charge a higher fee.

c.

When it is "at the money," the Exchange shuts down trading of the option contract.

d.

The Exchange will use mark to market accounting to record a loss.