I too selcted B but guess when a ''phenomenon'' is discussed it is treated as an ''entity'' N not as a ''time frame'' and that is why the use of in which '' suits better than the use of ''when''
entity= object or thing = in which
time frame= when
as for the second one I went wid D cos of two reasons: 1 always and always it is the best policy of ets to ''stick'' with the ''original'' part of the sentence when nothing else is better and hence '' by no means certain ..... expenditure of LARGE sums of money''
two: as some one already said '' expenditure of large sums of money '' is much better than ''expenditure of money ...''
also very minute aspect '' the use of certainity'' doe s not go well it is good to let the sentence flow in simple present and active voice and hence '' it is no means certain'' goes well...
hope that helps!
the whole worldmakes way for the man who knows wer he's going... good luck