SAT语法题the city of houston,texas,【is about sixty miles inland

although about sixty miles inland是一个省略句.完整的句子是：
Although it is about sixty miles inland,the city of houston,texas,is the third largest foreign-trade port in the united states.
尽管位于内陆60英里,德克萨斯州的休斯顿市却是美国的第三大外贸港口.
whose location is about sixty miles inland,makes it 从语法角度看没有问题.但意思上不对.港口城市一般临海,而休斯顿不靠海,没有成为外贸港口的地理优势.
明白了吗?

亲：这是一个省略主语和谓语动词（be）的结构，是的语言简练。
例如：I can do it well although (I am) young.
祝你学习进步！