Sat 语法Like former British prime minister MT,who studied chem

Sat 语法
Like former British prime minister MT,who studied chemistry in college,German chancellor AM was initially drawn to the sciences,(earning) a doctorate in physics before entering politics.
个人觉得括号里应该改成having earning a doctorate.但是答案说这句话没有错.求分析!

肯定是不能改成having earning a doctorate的,因为没有having earning这种表达结构.
我猜想,你是想改成having earned?
其实原句的主干是：German chancellor AM was initially drawn to the sciences and earned a doctorate.
显然,was drawing to 和earned是并列关系；如果要改写后面的earned,自然是改成earning.
你想改成having earned,应该是被你的中文翻译所困扰（进入政界以前,已经获得物理学博士学位）；如果按照你这种思路理解,是不是要将German chancellor AM was initially drawn to the sciences改为German chancellor AM had initially been drawn to the sciences呢?
所以没必要改成having earned.
再问： 啊，打字太急打错了。。。 Thanks a looot!!! 解释超好~~