下面的代码实现的效果是( ) < div class = " progress " > < div class = " progress-bar progress-bar-success " role = " progressbar " aria-valuenow = " 60 " aria-valuemin = " 0 " aria-valuemax = " 100 " style = " width: 6 0%; " > < span class = " sr-only " > 40% 完成 < div class = " progress-bar progress-bar-info " role = " progressbar " aria-valuenow = " 60 " aria-valuemin = " 0 " aria-valuemax = " 100 " style = " width: 30%; " > < span class = " sr-only " > 30% 完成(信息) < div class = " progress-bar progress-bar-warning " role = " progressbar " aria-valuenow = " 60 " aria-valuemin = " 0 " aria-valuemax = " 100 " style = " width: 20%; " > < span class = " sr-only " > 20% 完成(警告)