She came to visit the Greens ( ) they were having supper 填什么?是as before

She came to visit the Greens ( ) they were having supper 填什么?是as before
She came to visit the Greens ( ) they were having supper 填什么?是as before

She came to visit the Greens ( ) they were having supper 填什么?是as before
as
这里作连词（Conj.）
在…期间,当…时候
I was coming in as he was going out.
我进来的时候,他正出去.
你这道题的中文意思是：“她在格林夫妇吃晚饭的时候去拜访了他们.”
Before显然不对啦,因为你看要填的连接词后面的句子的时态和语态是过去进行时,特别是"having"这个进行时,为什么会用进行时呢?说明格林夫妇正在吃晚饭,而不是在吃晚饭之前,排除before.