activity of clay的用法和样例：
- The artist started with a big lump of clay.
- The president had feet of clay: he drank a lot.
- A sun-dried, unburned brick of clay and straw.
- The mass of clay was worked up into a reclining figure.
- I believed him to be honest but his actions showed that he had feet of clay.
- Bricks and dishes are made from various kinds of clay.