问一道题：NO.PZ2016082405000060，CCP的initial margin如何计算

Setting margin levels anloss reserves are important aspects of mitigating systemic risk through the use of a centrcounterparty (CCP). Whiof the following statements most accurately reflects the calculation of initimargins? The value risk (VaR) approasets appropriate initimargins the 99% confinlevel. The StanrPortfolio Analysis of Risk (SPAN) is consirethe most aancemethology toy in calculating initimargins. The calculation of the initimargin shoulbaseon volatility, tail risk, anpenncy. Initimargins pensolely on the cret quality of the clearing member. C  The calculation of the initimargin shoulbaseon volatility, tail risk, anpenncy. The value risk (VaR) approais a more aancemethoththe SPapproafor calculating initimargins. Stues suggest ththe Vapproaes a goojob of setting initimargins the 95% confinlevel, but the 99% confinlevel initimargins are not sufficient. The initimargin pen primarily on market risk annot the cret quality of the clearing member. 老师为啥不选B ，PPT上说美国和伦敦期货不是用SPAN计算初始保证金。