Query to find out records with non-duplicate of two columns combination

This is an extension for question:
https://www.experts-exchange.com/questions/28383519/Query-to-find-out-records-with-duplicate-of-two-columns-combination.html?anchorAnswerId=39914320#a39914320

I have two tables that have the same structure but data might be slightly different. Table names are a and b and column names to be used are c1, c2 (there are many other columns for table a or b)

Example:
select c1, c2 from a
c1 c2
2  UK
3  USA
5  Japan

select c1, c2 from b:
c1  c2
2   UK
3   USA
5   France

After the query, result should be (retrieve c1, c2 info from table a)
c1 c2
5 Japan

Again, please note: I need to compare combined fields of c1 + c2. It's assumed both table a and b have the same number of records and mostly identical