a - hemihydrates gypsum的用法和样例：
- Choosing potassium sulfate as an activator to stimulate the activity of natural anhydrite,and modified its properties by adding Portland cement and hemihydrate gypsum respectively.
- There is a vein of melancholy in his character.
- There was a long lag in forwarding mail to us.
- A bowl of hot chicken soup is good for you.
- A cloud is a mass of vapor in the sky.