You are correct that options d) and e) are not buffered solutions because they contain a strong acid, HCl. A buffered solution requires a weak acid or base and its conjugate base or acid.
Let's analyze the remaining options:
a) 0.10 M NaCl and 0.10 M NaNO2:
This mixture does not contain any weak acid or base, so it is not a buffered solution.
b) 0.10 M NaCl and 0.10 M NH4Cl:
This mixture contains NH4Cl, which is a weak acid, and its conjugate base, NH3. Therefore, this is a buffered solution.
c) 0.10 M CH3NH2 and 0.15 M CH3NH3Cl:
This mixture contains CH3NH2, which is a weak base, and its conjugate acid, CH3NH3+. Therefore, this is a buffered solution.
f) 0.1 M CH3COO and 0.15 M NaC2H5OO:
This mixture contains CH3COO-, which is a weak base, and its conjugate acid, HC2H5OOH. Therefore, this is a buffered solution.
So the correct choices for buffered solutions are b), c), and f).