For the new country to survive, ________ for its people to enjoy prosperity, new economic policies will be required.

When workers are organized in trade unions, employers find it hard to lay them ________.

Comrade Li ________ be in Beijing because I saw him in town only a few minutes ago.

曲线，渐近线的条数为（）

The wealth of a country should be measured ________ the health and happiness of its people as well as the material goods it can produce.