How to use these phrases

Dear UE's teachers !

Today I meet an uncomprehensible question when i do my English multiple-choices exercises.

And here is it:

Just in case our primary plan fails to succeed, I suggest we have an alternative plan_____
a/ at place
b/ in place
c/ on place
d/ by place

The answer is B: In place. I don't understand what it means and about the other answers.

Can i have more than 1 question? :) Does it (In place) mean the same as "In / Under (any) circumstances".

I'm very grateful for our help!

P/s: Sorry for my bad English!

It means that the alternative plan should be ready and that the people are in a position to implement it if they need to.

In place = ready, organised, prepared.

Tomorrow is my father's 50th birthday and everything is in place for the big party.
In case of emergencies, there is a contingency plan in place.
The bank robbers said that everything was in place for the heist.