Final answer:
To finish the project one day early, the completion time should be reduced by one day for each of the 150 jobs.
Step-by-step explanation:
To finish the project one day early, the completion time should be reduced by one day for each of the 150 jobs. This means that the expected completion time for each job should be decreased by one day.
So, the correct answer is (a) each of the 150 jobs.