a ca?canny policy的用法和样例：
- B: No, l'ho lasciata da due mesi e ora studio a Ca' Foscari.
- He took out a fire insurance policy for his house.
- By default, a certificate issued by a CA is only valid for 12 months.
- A family on a budget can't afford meat every day.
- You can't put a price on that sort of loyalty.