This passage comes from a high school textbook.

After the division, North Korea attempted to overthrow South Korea's government. When this proved impossible, the North Korean communists began to prepare themselves for war while pretending to negotiate peacefully.

On June 25, 1950, the north began its invasion of the south. The south was taken by surprise, but the armies of South Korea fought bravely to defend their liberties. This action moved the United Nations Security Council to declare the invasion by the north illegal and a threat to peace. A decision was made to help the south, and a UN army, led by the United States, Britain, and France, joined the South Korean forces in an effort to repel the invasion.

Which statement best describes the reliability of this source?

Its content is mostly reliable because it accurately describes how the war began.
Its content is mostly reliable because it describes the true cost of the war.
Its reliability is questionable because it supports the US and South Korean account
Its content is unreliable because it opposes the US policy of containment.