规则combine each group of sentences into a single setence,using coordinatin ,subordination or both
例如 Walden Pond is now the site of many tourist stands
It was once raised by Thoreau for its natural beauty
合并为Walden Pond which once praised by xxxxx is now the site xxxxx
要合并的句子是This is a good spot for picnic
A river flows on one side
A large tree provides shade
不好意思 少了一句 ~~~~
接上面 第三句是We can spread our blanket on the grassy knoll