Final answer:
The run-on sentence from the given choices is A. 'I didn't know which job I wanted, I was too confused to decide.'
Step-by-step explanation:
The correct answer is A. 'I didn't know which job I wanted, I was too confused to decide.' This sentence is a run-on sentence because it combines two complete sentences without any punctuation to separate them. To fix this run-on sentence, a comma or a coordinating conjunction like 'and' or 'but' could be added between the two complete sentences.