The table below shows a list of radioisotopes and their half-lives.

A 2-columns table with 10 rows. Column 1 is labeled radioisotope. Column 2 is labeled half-life. Lithium-5, 3 times 10 to the negative 22 seconds; polonium-211, 0.516 seconds; Barium-139, 82.7 minutes; uranium-240, 14.1 hours; Bismuth-210, 5.012 days; uranium 232, 68.9 years; carbon-14, 5730 years; plutonium-239, 24,065 years; beryllium-10, 1.6 times 10 to the 5 years; uranium-238, 4.5 times 10 to the 9 years.

The radioisotope that has the longest half-life is the best to use in powering planet and space exploration vehicles because they can travel farther. Which radioisotope is the best to use?
lithium-5
uranium-240
carbon-14
plutonium-239