languages parsed with recursive descent

Question

I was wondering what makes languages possible to be parsed with recursive descent. for example we have 5 languages over {x,y,r}:

A = { x^n y^n | n <= k }
B = { x^n y^k | n > k }
C = { x^k y^n | k > n }
D = { x^n y^n r^n | n <= k }
E = { x^n y^n r^n | n >= k }

where there are n occurences of x,y,r and k is unknown.

My reasoning is that only if we can define the language with a context free grammar then it can be parsed with recursive descent and if that is the case I think only B and C are possible to be parsed with recursive decent but I am not sure

Answer 1

I believe that for L1, it is possible to parse in recursive descent as it would be possible to recognise for a DPDA.