why DoEs thE Author mEntion thE siErrA nEvADA in linE 10
A．to ArguE thAt A mom DirEst routE to thE wEst CoulD hAvE Boon tAkEn,
B．to iDEntiFy A historiCAlly signiFiCAnt mountAin rAngE in thE wEnt,
C．to point out thE lEgAtion oF n sErious trAin ACCiDEnt,
D．to givE An ExAmplE oF An oBstAClE FACED By thE CEntrAl pACiFiC.