You should d________ the thief carefully to the policem...

根据句子结构，‘You should ______ the thief carefully to the policeman’中的‘carefully’提示需要一个动作，‘describe’意为‘描述’，符合句子意思，意思是要仔细地将小偷描述给警察，这样他就能尽早被抓住。