Final answer:
Sherman shows Penny the WABAC to fix an issue caused by buffalo chips and also to explore different time periods or find answers to their questions.
Step-by-step explanation:
Sherman shows Penny the WABAC because in the text it is mentioned that someone tucked buffalo chips into Meriwether's knapsack when he wasn't looking. This suggests that the WABAC, a time machine, is used to go back in time and fix the issue caused by the buffalo chips. Additionally, the text mentions that after a long journey, Sherman and Penny wanted to find a name for a fruit, which implies that the WABAC is used to travel to different time periods and explore different topics or find answers to their questions.