a foam mattress的用法和样例：
- Massive fatigue attacks were used, requiring Eleanor to actually lie down on a foam mattress during the work day at times.
- Why can the soap produce a foam?
- Mary： Today, I'll try a foam perm.
- I might as well try a foam perm.
- An eerie breeze caressed his cheek as the blankets dropped empty and silent to the foam mattress.