A 75 is the lowest passing score for any section. However, your total average must be above a 75 in order to have a complete pass. If just one of the 4 scores is below a 75, but your overall average is above a 75, then you only need to retake that one part of the exam.
So, a score of 75, 76, 75, 75 is a full pass because the average is above a 75. However, scores of 85, 73, 70, 71 is a complete failure because the average is below 75 (even though you got an 85 in one section, you must retake the entire exam).