An army spokesman stressed that all the soldiers had been ordered ________ clear warnings before firing any shots．

A.to issue

B.being issued

C.to have issued

D.to be issued

答案及解析： A

解析：

本题考查不定式作主语补足语的用法及非谓语动词的时态和语态。order sb．to do sth．命令某人做某事句中的order是以被动形式出现的，故其后应接不定式作主语补足语。又因issue（发布）的宾语是clear warnings，且该动作尚未发生，故选不定式的一般式作主补。