Answer: The correct answer is option (4)
Step-by-step explanation:
Nuclear waste is a waste material left after the use of nuclear material in a nuclear reactor. The waste material left behind is higher in radio-activity that is the waste is radio-active in nature. This waste is highly toxic in nature.
Being possessed by radio-active nuclear substance they have long half-lives which allows them to be remain radioactive for extended periods of time.
Their ability to be remain radioactive for extended periods of time poses a great problem for the experts.