a sofa that is convertible的用法和样例：
- a sofa that is convertible (into a bed)
- A sofa that is convertible(into a bed)
- In the portrait he is shown lying on a sofa.
- A sofa that converts into a bed;arms factories converting to peacetime production.
- A sofa that looks just right in the store, might look too big in your room or not big enough.