Explanation:

- Option 1: Activated by man: This suggests human intervention is needed to activate radium. Incorrect, since radium's radioactivity is inherent and not reliant on external activation.

- Option 2: Naturally activated: Radium is naturally radioactive. This means its radioactivity is an intrinsic property, occurring without external influence. This is the correct description of radium.

- Option 3: Chemically activated: This implies chemical reactions would trigger radium's radioactivity. Radium's radioactivity is due to its atomic structure, not chemical changes, making this incorrect.

- Option 4: Absolutely inactivated: Incorrect, as radium is well-known for its natural radioactivity; it is far from inactivated.