Which of the following pairs of substances, when mixed in any proportion you wish, can be used to prepare a buffer solution?

Question

1)NaCN and NaOH
2) HCl and NaOH
3) HCN and NaOH
4)HCl and NaCN
5) NaCN and HCN

is the answer 1 and 5??

Answer 1

I don't believe 1 will do it.
Yes on 5. Also 3.
Buffers are weak acid and salt or weak base and salt.
HCN and NaOH can prepare the salt and have HCN left over.
NaCN is the salt HCN for the acid.

Answer 2

I tried those and it was wrong

Answer 3

1,3,5 will do it

Answer 4

1-No
2-No
3-Yes
4-Yes
5-Yes