痉挛的原因是
A．γ、α运动神经元敏感性增加B．牵张反射亢进C．对侧伸肌反射亢进D．整个脊髓反射亢进E．屈肌反射亢进
参考答案：D
清雍正朝以后，清皇室内部百余年再未发生倾轧夺位的重大事件，其主要原因是从雍正开始实行（）。
One year ago, an investor purchased a 10-year, $1000 par value, 8% semiannual coupon bond with an 8% yield to maturity. Now, one year later, interest rates remain unchanged at 8%. If the investor sells the bond today (immediately after receiving the second coupon payment, and with no transaction costs) he will have a capital:（）
A. gain of $80.
B. loss of $80.
C. gain of $0.
