HZ star

例句：

1. 1. The equation has two unknowns: x and y.
   这个方程有两个未知数：x和y。
2. 2. The answer is a hyphenated word, which means "and".
   答案是一个连字，意味着“和”。
3. 3. The question mark indicates uncertainty in the text.
   问号表示文本中的不确定性。