Teaching English

A missionary was finishing his tour of duty and was about to leave his mission in the jungle where he had spent years teaching the natives, when he realized the one thing he had never taught them was how to speak English. So he took the chief for a walk in the forest.
He pointed to a tree and said to the chief, "This is a tree." The chief looked at the tree and grunted, "Tree."
The missionary was pleased with the response. They walked a little farther and he pointed to a rock and said, "This is a rock."
Hearing this, the chief looked and grunted, "Rock."
The missionary was really getting enthusiastic about the results when he heard a rustling in the bushes. As they peeked over the top, they saw a couple of natives in the midst of heavy sexual activity.
The missionary is really flustered and quickly responded, "Man riding a bike."
The chief looked at the couple briefly, pulled out his blowgun and killed them.
The missionary went ballistic and yelled at the Chief that he had spent years teaching the tribe how to be civilized and kind to each other, so how could he kill these people in cold blood that way?

The chief replied, "My bike."