用所给单词的适当形式填空 1. There are _______ (milli

问题：

用所给单词的适当形式填空

1. There are _______ (million) of birds in the forest.

2. You _______ (fail) the exam unless you work hard.

3. The cake _______ (make) by my mother yesterday.

4. The abacus was invented in the _______ (six) century.

5. I _______ (know) nothing about it until you told me.