Some properties of the p-t-reducibility and the sn-t-reducibility are prese-nted.For example

1.As NP and NPC are presentable (see[3])

and we haveshown here that there exists a set AεNP-P such that P~A(?)NP NPC under theassumptions that P≠NP and NP=co-NP

we ask if there exists a set A suchthat P~A=NP-NPC

We sak if there ehists a set A such that P~A=NP-NPC

or more generally

if NP-NPC is recursively presentable.We prove thatNP-NPC(?);2.We prove that there exist p-t-incomparable sets inEXP.As the best technique known for simulating deterministically anondeterministic polynomial time

it might be of some interests;3.Long (see[4]) showed that if NP≠co-NP

then for each BεNP-co-NP

there is a set AεNP-co-NP such that A(?) B.We consider this kind of problems in right direc-tion and we prove that for each A there exists B such that A(?) B

and ifNEXP~A=co-NEXP~A then BεNEXP~A.