your father [ ][finish]his work just now 用过去时和现在完成填空

你爸刚刚完成工作

have finished

此处应用过去时.
just now作“刚才”、“一会儿之前”解时,常与一般过去时连用,位于句首或句末；它也可指“（加重语气的）现在”或“片刻之后”,这时可用于现在时或将来时.如：
They gave it to me just now．他们刚才把它给了我.
I'm busy just now．我现在很忙.
I'll tell you a story just now if you have time to listen to it．
如果你有时间,我马上就把故事讲给你听.
just now 有三种含义：
1、at this moment 此时、此刻、眼下
Come and see me later,I'm busy just now!
过些时候再来,我这会儿正忙着呢!
2、during this present period 目前；现阶段
Business is good just mow.
目前生意很红火.
3、onlu a short time ago 刚才；刚刚；一会儿前
I saw her just now.
我刚刚见到过她.
因此此处应用过去式finished.