__ in the company for three years, Mark has business negotiations（）
A. Having worked
B. Having been working
C. Have worked
D. Worked
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Web前端开发技术中HTML是用来完成网页内容的，CSS是用来设置样式的（）
A. 正确 B:错误
后端部分是对普通用户不可见的，例如从数据库中读取数据（）
A. 正确 B:错误
When you are giving the speech, what you should do in the introduction section（）
A. Set the tone
B. Creat interest
C. introduce the topic
D. Grab attention
What are the introduction techniques in presentations which are mentioned in the video clip（）
A. Tell a personal story
B. Ask a question
C. Startling statements
D. Invite a clown to do the opening for you
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