, I believe option C is valid. See, two countries might have been at war, or not - we do not know. So we cannot infer this from the passage.
Coming to option A, when Portugal took complete ownership of Angola, it was only them who could do the trading (buy or sell) of minerals and slaves. So, option A can be inferred. Hope this helps.
Sajjad1994
Official Explanation
1. Which of the following is NOT stated as a component of Portugal and Angola’s historical relationship?
Explanation
You are asked for the choice NOT in the passage. You are told that Portugal once mined Angola for slaves and raw material, so (A) and (B) are out. The beginning of the passage concerns Portugal taking over Angola over a period beginning in the 16th century and culminating in the 1920’s, so kill (D). The passage refers to Angolan independence in 1975 — since that date is during the 20th century (1900’s = 20th century, 2000’s = 21st century, etc.), kill (E). You are told that a civil war in Angola lasted until 2002, not a war against the Portuguese, so (C) is the answer.
Answer: C
Sajjad1994 - The passage only mentions that Angola was mined for slaves.
Nowhere in the passage does the author clearly mention that a) they were mined by Portugal traders b) they were further sold by the Portugal authorities.
Knowing that GMAT plays with modifiers and nuances like these, how can we accept option A as a clear inference from the passage?
Additionally, Option C seems more logical - For 3 centuries, Portugal tried to enter Angola, and bw 1920 - 1975 the colonization was reversed, how can we then say that we can't infer that the 2 countries were at war?