Answer:
The answer is A. threat to sovereignty.
Step-by-step explanation:
Unocal is Union Oil company of California. This is an organization which is like a body , comprises of many oil companies. Taking over of this organization by a foreign company will be a threat to US. This is because, the board of directors, agents, group and affiliates of Unocal will be controlled by the owner. And this will be a threat to supreme power of authority in US.