When 1 Peer decide to close their channel on a pentagon, What impact will be incurred as that result?

They should receive a bad rating. Otherwise the rest of the channels can remain open. They are still useful. 

can you please give me more details.  I have opened channel with C will this mean we will become a square.  If not can you please make it do so..Thank you

Yes. I can turn it into a square, but not necessary. There is no problem if one participant drops out the remaining channels remain operational. You don’t have to route in a shape. You route on any channels regardless of a swap.