Final answer:
The high pH buffer showed the least pH change when basic 0.1M NaOH was added because it had a higher buffer capacity.
Step-by-step explanation:
A buffer solution maintains a relatively constant pH even when acid or base is added to it. The high pH buffer showed the least pH change when basic 0.1M NaOH was added because it had a higher buffer capacity. Buffer capacity is the ability of a buffer to resist changes in pH when an acid or base is added. The high pH buffer had a greater concentration of the buffer components, which allowed it to absorb and neutralize more of the added base, resulting in a smaller pH change.