- 袋中有 3 个红球， 2 个白球，第一次取出一球后放回，第二次再取一球，则两球都是红球的概率是 ( )
- 若线性方程组AX=0只有零解，则线性方程组AX=b( )．
- 向量组的秩是 ( )．
- 设 A，B 都是 n 阶矩阵 (n>1) ，则下列命题正确的是( )．
- For the new country to survive, ________ for its people to enjoy prosperity, new economic policies will be required.
- She had clearly no ________ of doing any work, although she was very well paid.
- The wealth of a country should be measured ________ the health and happiness of its people as well as the material goods it can produce.
- When workers are organized in trade unions, employers find it hard to lay them ________.
- It's more ________ to buy a season ticket if you travel every day.
- To study a foreign language, __________.
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