用所给词的适当形式填空。

1. Australia has beautiful ___________ (beach).

2. I eat supper with my ___________ (family).

3. Canada's flag has a ___________ (leaf).

4. This is ___________ (Australia) flag.

5. What colour are ___________ (it) stars?

6. ___________ (kangaroo) live in Australia.

获得性免疫缺陷病的重要免疫学特征是 （）

A.CD3⁺细胞数量下降

B.CD8⁺细胞数量下降

C.B细胞功能亢进

D.CD4⁺细胞/CD8⁺细胞比值倒置

E.血浆免疫球蛋白水平降低