D.A.

例句：

1. 1. He is a doctor of arts and sciences, specializing in environmental science.
   他是一名艺术与科学博士，专攻环境科学。
2. 2. She earned her Ph.D.in physics from MIT.
   她从麻省理工学院获得了物理学博士学位。
3. 3.The doctor of arts and sciences has been working on this project for several years.
   这位艺术与科学博士已经在这个项目中工作了好几年。