A semi-log plot of the number of undecayed nuclei N versus time never meets the time axis. Which one of the following is the correct explanation?
(a) Because the detector cannot register the last few surviving nuclei, the plotted value of N never appears to reach zero
(b) The probability of decay in any finite time interval is less than 1, so N approaches zero asymptotically
(c) Since logN is undefined at N=0, a semi-log graph cannot physically show the curve touching the time axis
(d) A small fraction of the nuclei are assumed to be inherently stable, leaving a non-zero residue on the graph