{{i}}quEstions 17—20 ArE BAsED on thE Following tExt ABout A FirEFightEr. you now hAvE 20 sEConDs to rEAD quEstions 17—20.{{/i}}

how long DiD hErBErt rEmAin unConsCiousA．two AnD A hAlF months.
B．FiFty yEArs.
C．thirty yEArs.
D．tEn yEArs.