The appropriate particle

[farrelferdian]

So I stumble upon this question on my japanese language exercise.
木曜日( )ごご病院は休みです.
So what's the right particle to fill in the blank? The question allows no particle for the answer and I recon that's the right answer, but I'm not so sure.

 

[Majestic]

no particle works
の also works. I don't know which is better. I think they are both equally valid.

 

[farrelferdian]

no particle works
の also works. I don't know which is better. I think they are both equally valid.

I see, thank you so much!