Given the following table of product defects by manufacturing line, which line consistently had the lowest percentage of defective units over Q1 and Q2?

✓ Correct Answer: Option D

Line D has a consistent 2.5% defect rate. To determine the 'lowest consistently', one would compare the average or consistent performance. Line D's consistent performance is lower than the average of A (2.5%), B (2.5%), and C (2.5%), as other lines had higher spikes.