a painless injection的用法和样例：
- But it has not been a painless transition.
- CT has a specality on diagnosing cystic mass for its high resolution and CT guided ethonal injection was a painless.
- The most common presenting symptom is a painless mass.
- A cataract is a painless clouding of the lens of the eye.
- Becomes a painless and effective aspect of your development practice.