How did the speaker comment on Gerome’s speech

A．Gerome spoke last but not best.

B．Gerome spoke last but the best.

C．Although last, Gerome spoke fast.

D．Gerome spoke at a speech.

原燃料强度变差，粉末多，矿石种类复杂，化学成分波动大，特别是含钾、钠等碱金属有害元素多，是造成高炉结瘤的主要原因。