should have been doing是過去完成進(jìn)行時。
should
aux. 應(yīng)該；就；可能；將要；本當(dāng)；竟然
例句：
Six bottles should be enough.
六瓶應(yīng)該夠了。
The cloth should be laid flat.
布應(yīng)展開平放。