​Which of these is characteristic of movement training designed to develop flexibility?

A) ​It involves sudden, fast movements and bouncing.
B) ​It involves slow, sustained, stretching movements.
C) ​It involves more intensity than endurance training.
D) ​It involves greater intensity than strength training.

Movement training designed to develop flexibility typically involves slow, sustained, stretching movements, which aim to gradually increase the range of motion of the joints and prevent injury. Sudden, fast movements and bouncing should be avoided as they can cause overstretching and injury. Additionally, flexibility training typically involves less intensity than both endurance and strength training, as the goal is not to build muscular strength or cardiovascular endurance, but rather to improve joint mobility and range of motion.