可控硅和半导体二极管一样具有单向电性，但其（）是可控的。
参考答案：开始导通时刻
An analyst does research about margin transaction. An investor purchases common shares at $ 25 per share on margin and deposits just enough money to cover the 65% initial margin requirement. If the maintenance margin requirement is 30%, the share price below which the investor will first receive a margin call is closest to:（）
A. $11.54
B. $12.50
C. $19.70
若患者门诊化验肝功ALT260U/LTBIL46μmol/L；HBsAg阳性、HBeAg阳性、抗HbclgM阳性。临床应诊断为
A．病毒性肝炎、乙型、慢性轻度B．病毒性肝炎、乙型、慢性中度C．病毒性肝炎、乙型、慢性重度D．病毒性肝炎、乙型、急性重型E．病毒性肝炎、乙型、慢性重型
