同学你好，该知识点来自沪江网校《BEC商务英语中高级【四项全能实战签约班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学好
However一般用于句首或者句中
用在句首，前面是句号， 后面要加逗号
用在句中，前面和后面都要加逗号

例如：
1. I thought those figures were correct. However, I have recently heard they were not.
   我原以为那些数字正确无误，不过我最近听说并不正确。

2. Later, however, she decided to buy it.  可是后来她决定去买下它。

所以练习题中，最标准的写法应该是：
My parent want me to become a doctor, however, I am interested in Astronomy.
或：My parent want me to become a doctor. However, I am interested in Astronomy.

希望能帮助到你，祝学习愉快！