单项选择题Which tip is not mentioned in Part 3? A、Try to relax if you feel nervous. B、Make your speech as concise as possible. C、Have good body language. D、Speak at a comfortable speed.
单项选择题硼砂与水的反应是: B4O72-+5H2O=2H3BO3+2H2BO3- 用硼砂标定HCl时,硼砂与HCl的化学计量比为 ( ) A. 1:1 B. 1:2 C. 1:4 D. 1:5
