a slate quarry的用法和样例：
- You must have a slate loose this morning.
- The list so settled it now a slate, unless some discontented magnate objects and threatens to withdraw. To do so is called "breaking the slate".
- He's out on active service, wiping something off a slate.
- The innkeeper scored up the man's indebtedness on a slate.
- He's out on active service,wiping something off a slate.