以下哪一个指标可以反映单个证券相对于市场证券组合的变动程度，并用于衡量单个证券的系统风险（）。
A、αItisimportantto________yourskinfromtheharmfulstrongsunlight.
Veryfewpeopleunderstoodthiscontract,______wasveryobscure.
Wehopedtobeabletomoveintoournewhouseattheendofthemonth,butthingsdidn’t______asweexpected.
Bothofmybrothersarenowmarried，soIhavetwo_____.
重写句子：Theteacherreturnedthehomework.Theteachernoticedtheerror.(complexsentence)
