从事自营业务的证券公司可以自主决定是否买入或卖出某种证券，交易行为具有自主性．
参考答案：UNKNOWN
Junk messaging has been a headache for years, ＿＿the action taken by the authori-ties has not yet produced the results expected
A．as
B．but
C．so
D．before
没有设置重复，也能进行显著性检验。
