中国进出口商品交易会即广州交易会，简称广交会。每年举办（   ）次。   

现代农民充分利用自然条件，建立适合本地的生态农业系统的良性循环模式：蔗基鱼塘和桑基鱼塘．右图是蔗基鱼塘和桑基鱼塘的模式图，据图回答下列问题：

    Mrs．Marks bought a printer yesterday．She was h____ because she could print anything she wanted at any time．H____,after about an hour, she was angry because she couldn't print the color blue．All the other c____ printed free, except(除了)blue，which was very unusual．

    She d____ to call the after-sales service department(售后服务部)to help her solve the problem．David answered the phone．He t____ everything he could think of to help Mrs．Marks．He asked her to reinstall(重新安装) the program，to reboot (重新启动)the computer and to turn the printer on and off．N____ of these things helped．

After hours of trying，the problem s____wasn't solved．Finally, David asked Mrs．Marks if he could go to her h____and try to solve the problem in  person．Mrs．Marks agreed and t____ him her address(住址)．When he arrived at her house，she showed him her computer and the printer. David u____what the problem was right away．He told her,“From now on，print on white paper instead of blue!”