解：设快车开出x小时后两车相遇，根据题意得：

Who will you get ____(accompany) you on the piano at the school concert?

If there are ______ trees, the air in our city will be _______ cleaner.

    Everybody, welcome to ____(we) company. I am Luisa, Director of the department. Let me say something to you all. The starting of work can be exciting on the hand, and can also be ____(worry) on the other. No matter what your future job is, you will have to work with others. Leaning to get on well with others must come first,____ (include) all staff in the company and our ____ (custom).

    And secondly, right after my introduction, spend some time reading the introduction of our company and get to know the people in your office and find out ____ the company is like. This afternoon you can walk around our workshops and know ____ (much) about the products. No one is allowed ____ (leave) the company before 5:30 pm. By the way, lunchtime ____ (come) at 11:50 and it's free ____ charge.

    Remember: Learning is so important ____ it can change your future life.

This is what I'd like to say to you at the moment. If you still have any question, please come to my office. Thank you.

某溶液中可能含有SiO₃^2﹣、OH^﹣、CO₃^2﹣、SO₄^2﹣、AlO₂^﹣、HCO₃^﹣、Na⁺、Mg²⁺、Fe³⁺、Al³⁺等离子．当向该溶液中逐滴加入一定物质的量浓度的盐酸溶液时，发现生成沉淀的物质的量随盐酸溶液的体积变化如图所示．下列说法正确的是（　　）