Cs-gcl (registration of documents, 1908)

Please solve -

Question-

A executed a document on 20th oct, 2007 in favour of B. Therafter, executed another document on 11th dec, 2007 in favour of C in respect of the same property. The document b/w A and B was registered on 15th jan, 2008 whereas the document b/w A and C was registered on 15th dec, 2007.

Which document gets priority and why?

Ans.- The deed which executed first has priority or the document which is registered first will get priority.

( please explain with reason)