Which one of the following poets wroteThe Pilgrim’s Progress?
A、 John Milton
B、 John Suckling
C、 Richard Lovelace
D、 John Bunyan

A.滴定开始前
B.滴定至溶液呈浅黄色时
C.在标准溶液滴定近50%时
D.滴定至溶液红棕色退去，变为无色时