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E3C12:Which of the following is indicated by a sudden rise in radio background noise across a large portion of the HF spectrum?

E3C12E3C

Which of the following is indicated by a sudden rise in radio background noise across a large portion of the HF spectrum?

Direct answer summary (2024-2028 NCVEC pool)

The official correct answer for E3C12 is A coronal mass ejection impact or a solar flare has occurred.

The key fact is A coronal mass ejection impact or a solar flare has occurred. Match that fact to the exact condition in the question; the other choices describe a different rule, band, component, or operating situation.

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