While it may have done any of those, the most correct answer is D.
If ‘scientific management’ could be said to be one thing, it would be breaking with tradition and finding the best way to do things. Anything.
One of the things it did was to clarify expectations and qualifications for jobs. People weren’t hired just because their family did something, but instead they had to prove they were the best person to do it. It also rewarded people for doing better or more work, instead of giving a traditional rate. In these senses, it might have eased stress or improved relations, though it other senses it might have made things worse, depending on your point of view.
One of the goals was efficiency and cost effectiveness. So it certainly may have improved coal shoveling and any number of other enterprises. But again because of individual differences, it may sometimes have made things worse – if your employer decides right-handed people do a job better and you’re not right-handed, then you either adapt or find a different job (no matter HOW good you are at left-handed shoveling).
These two things may seem to contradict… but keep in mind that all the parts of a factory are interrelated. A left-handed shoveler requires different accomodations than a right-handed one. Which means you either have two sets or you figure out which one way is best. As I’ve tried to show, this can be both a strength and a weakness.
Some even suggest that implementation of ‘scientific management’ (and treating employees like cogs) was one of the larger reasons for the rise of labour unions…

D… and that’s my final answer.