Friendship is an important way to obtain happiness in life. According to the ancient Roman philosopher Cicero, "friendship only exists between good people, and friendship that lasts forever is the hardest thing"; another Spanish philosopher Jolo Shangtayana believes that "friendship is almost always a combination of part of one heart and part of another heart, and people can only be partial friends. ". If the above statement is true, Which of the following must be true. ['Life-long friendship is the most precious asset.', 'There must be no friendship between bad people and bad people.', 'There must be some kind of local friendship between good people.', 'Friendship is the most important way to achieve happiness in life.']