求助！遭遇保底学校老师逼宫，该怎么办？

之前被反套，联系了几次，老师就来邮件逼宫，求助各位高手，我该怎么回复？毕竟是第一个offer，我还不想放弃啊。
这是老师发来的邮件：
I am planning to offer an research assistantship to you. Before I
start the paperwork, I want to check with you to make sure that
you once you receive the offer, you will accept the offer and will
come here, with a goal of finishing the Ph.D. degree.

拜谢各位了~