Step 1: Understand the Outer Space Treaty.
This treaty is the foundation of international space law.
Step 2: Analyze the statements based on the treaty's principles.
(A): This is incorrect.
Article II of the treaty explicitly forbids national appropriation of outer space.
Space is the "province of all mankind.
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(B): This is incorrect.
Article IV expressly prohibits placing nuclear weapons or other WMDs in orbit.
(C): This is correct.
Article I of the treaty states that the exploration and use of outer space shall be carried out for the benefit of all countries and shall be free for exploration and use by all States without discrimination of any kind.
(D): This is incorrect.
Article V states that astronauts shall be regarded as "envoys of mankind" and states must render them all possible assistance.
States retain jurisdiction over their nationals, but the concept is broader than simple nationality rules.