Which of following is the best way to correct this run-on sentence?
The dog chased its ball into the lake he could not get it.
A. The dog chased its ball into the lake, when he could not get it.
B. The dog chased its ball into the lake. But he could not get it.
C. The dog chased its ball into the lake. And he could not get it.
D. The dog chased its ball into the lake, but he could not get it.