few things could be more impressive than the peace that descends on deserted city streets at weekends when the thousands that travel to work everyday are tucked away in their homes in the country. be tucked away是被动吗 如果是 后边为什么加away
语法上，一个简单句只能有一个谓语 they saw great stalagmites中的saw已经作谓语了 中间的插入语，不能加be动词，加了的话中间的插入语也有主语、谓语，也是一个单独的简单句了 插入语不能是一个完整的简单句，只能是一个短语 所以，中间的插入语some of them over forty feet high-rising up like tree不能加be动词作谓语 ，要加只能加being，慢慢思考分析一下，会明白的。追问