根据短文内容，完成所缺的单词。（5分）

It’s not    1  to be the same. I like to have friends who are    2   from me. My best friend Larry is taller and more outgoing than me. We    3  like sports, but Larry is                                                                              

4   athletic than me. He    5   beats me in tennis. Also, I’m quieter than he is.

硫酸镁抗惊厥的机制是

A．降低血钙的效应

B．升高血镁的效应

C．升高血镁和降低血钙的联合效应

D．竞争性抑制钙作用，减少运动神经末梢释放乙酰胆碱

E．进入骨骼肌细胞内拮抗钙的兴奋-收缩作用