单选题 According to the passage how many miles long was the trench that became known as the Grand Canyon?

【正确答案】 B

【答案解析】第三段倒数第二句话说“然后，新的河流开始切割出最后成为大峡谷的长达277英里的壕沟来”，因而本篇作者认为大峡谷长227英里，故选[B]。