Answer: 1. destabilize ----> to make a nation lose face with its people, thereby causing its downfall.
2. détente ----> a lessening of mistrust or hostility between two people or nations.
3. inadvertent ---> something done by accident or without malice.
4. rift ---> a breaking- or splitting-up between two friends.
5. stagnant ---> to stand still or be unmoving.
Explanation: "Destabilize" means to cause instability. In most cases, this word is used to refer to the functioning of a government. On the other hand, "détente" makes reference to an improvement in the relationship that exists between two nations. It has been mainly used to describe a phase in the Cold War. Moreover, "inadvertent" is an adjective that depicts an action as unintentional, that is to say as done by accident, and "rift" is a noun that refers to a strong disagreement between two people which causes a splitting-up. Finally, "stagnant" is used to describe a situation or a business that shows little or no activity at all. Therefore, "stagnant" describes something that does not grow.