What do the confidence intervals indicate for these four regimens?
Study A has confidence intervals that are above the "null" value of no change in diastolic blood pressure, but overlapping the range of clinical indifference (the range over which you would not choose to do anything differently). It is above the "null" value and, hence, has statistical significance, but most of the range lies within the clinical indifference zone, so there may be no practical significance. Perhaps, a larger study population would show practical significance to this regimen.
Study B does not overlap the "null" value and is entirely above the range of clinical indifference, so it has results that are of clinical and practical significance.
Study C overlaps the "null" value and the results probably have no clinical significance, but a larger study might show significance.
Study D overlaps the "null" value and is entirely within the range of clinical indifference, so it has no significance.