The correct answer is D) Long splice. The long splice is used to connect two separate lines together to create a continuous length. This is the preferred method for joining two lines, as it distributes the load evenly and creates a smooth transition between the two lines. The long splice is stronger than the other splice options and does not significantly increase the diameter of the joined lines. The other answer choices are incorrect because they serve different purposes - the back splice is used to create an eye or loop at the end of a line, the chain splice is used to connect the end of a line to the middle of another line, and the eye splice is used to create a permanent loop or eye at the end of a line.