The correct answer is option 4 - gains momentum.

Running before jumping allows the long jumper to gain momentum, which is essential for a successful jump. Momentum is the product of an object`s mass and its velocity. By running, the long jumper increases their speed, which directly increases their momentum. This increased momentum enables them to jump further.

Option 1 - covers a greater distance: While it is true that the long jumper will cover a greater distance during their jump, this is not the primary reason for running before jumping. The main purpose is to gain momentum, not to cover a greater distance on the ground.

Option 2 - maintains momentum conservation: Momentum conservation refers to the principle that the total momentum of a system remains constant. This option does not explain why the long jumper runs before jumping.

Option 3 - gains energy by running: Although running does provide some additional energy to the long jumper, this energy is converted into momentum. Running alone does not explain why the long jumper runs before jumping.

Therefore, option 4 - gains momentum is the most accurate explanation for why a long jumper runs before jumping.