编辑以下句子中的语法错误：“She was laying on the couch and reading a book”（她躺在沙发上看书）
"She was laying on the couch and reading a book"（她躺在沙发上看书）
"She was lying on the couch and reading a book." （她躺在沙发上看书） 

"Laying" 是过去式的 "lay" 的现在分词，应该用 "lying" 来替代，“lying”是 “lie” 的现在分词。