Important consequences of the impossibility of complete testing are
We can never be certain that the program is bug free
We have no definite stopping point for testing, which makes it easier for somemanagers to argue for very little testing.
We have no easy answer for what testing tasks should always be required,because every task takes time that could be spent on other high importance tasks.
The impossibility of complete testing has three critical consequences: we can never guarantee bug-free code (A), testing lacks a definitive stopping point allowing managers to under-test (B), and every testing task competes with other priorities for time (C). Since all three statements are valid consequences of exhaustive testing being impossible, 'All of the above' is correct.