When I arrived she greeted me at the door, her kids all ( ) be

When I arrived she greeted me at the door, her kids all ( ) behind
A、standing
B、stood
C、have been standing
D、were standing
【正确答案】：A
【题目解析】：独立主格主语+ving./v-ed./adj./adv.，我到时，她和我打招呼，她的孩子们站在后面。