[BaO]

which of the following can make a acidic buffer solution ?

A H₂S and NaHS
B NH₃ and NH4Cl
C HNO₃ and some thing, 
D somthing and H₃O⁺
 i dont remember C and D but they are obviouly wrong, righ?

 there are A and B left,  i calculated the pH of B , it`s around 9 or something. so the answer is A
but it`s weird , i got 7.0 for the pH of A which makes the solution neutral.
what`s wrong now 

[BaO]

oh nevermind , i know what's wrong now, the answer should be D , H₃O⁺ and H₂O , or is it?

[Borek]

Strange question. Some of these solutions can be acidic, but I will not call them buffers in the classic sense.

[BaO]

Some of these solutions can be acidic

really? so you meant the way i calculated the pH for those solutions was wrong :

i calculated the pH of B , it`s around 9 or something. so the answer is A
but it`s weird , i got 7.0 for the pH of A

but I will not call them buffers in the classic sense.

why?

[Borek]

C solution will be acidic for obvious reasons and it will have some buffer capacity. But HNO₃ is too strong to be the buffer in the classic sense (even if it is the weakest of the strong acids).