• need to do sth和need d...
• begin to do sth和begin...
• finishdoingsth和finish...
• to do sth和 doing sth作...
• to do sth和 doing sth作...
• finish doing sth和fini...
• to_do用法
• need to do sth实义动词
• to do 结构
• 语法“to do”