读下图，甲、乙、丙三地的气候类型都是（   ）

如果把玻璃罩里的空气抽掉，里面成了____，我们就只看见闹钟的铃在动，却听不见声音。

House of noodles
    We have three size bowls of noodles, small, medium and large. A small bowl of mutton(羊肉) and carrot noodles is RMB 5. A medium bowl of beef and potato noodles is RMB 7. A large bowl of chicken and cabbage noodles is RMB 8.
Welcome to our house.
Lunch special
    We have some great specials. The cabbage, tomatoes and rice lunch special is RMB 3. The beef, carrots and rice lunch special is RMB 5. The dumplings and soup lunch special is RMB 8.
Time: 11:00a.m---2:00p.m
Dessert house
    What kind of dessert would you like? We have two new specials: ⑴ Apple, strawberry and ice cream. ⑵ Banana, orange and ice cream. And what size of dessert would you like? Small, medium or large? And we also have juice and tea.

四棱锥P﹣ABCD的底面ABCD为正方形，PA⊥底面ABCD，AB=2，若该四棱锥的所有顶点都在同一球面上，且该球的表面积为$\frac{81\mathrm{\pi }}{4}$，则该棱锥的高为（　　）