have u seen a pen

1. Is it a black one?
填a, 因为只有在说话双方都知道那支钢笔的时候才用the,即the表示“特指某支钢笔”,而这句话“是一支黑色钢笔吗?”,属于“非特指”,因此用不定冠词a
2. 选 C
A fire broke out last night. They managed to put out the first soon.
【解析】
首先,“昨天夜里发了一场大火”,为非特指,说话的人只是说“有场大火”,因此用a
其次,在序数词、最高级之前一定用the,这是规定,the first, the second, the best, the most beautiful. 记住这个规则就好.