who
that
for whom
to whom
本题考查定语从句引导词的选择。从句还原语序为he has set a good example to the young fan.先行词在从句中作宾补，故选D。
句意：这位歌手收到一封年轻粉丝的来信，说他给粉丝树立了一个好榜样。
