13.A line connecting points of equal magnetic variation calls ___________ . (A)magnetic latitude (B)magnetic declination (C)deviation (D)isogonic

8.翻譯：危險急迫嗎？是的，有穩定度減小的危險。 (A)Is danger imminent? Yes, danger of damage by sea. (B)Is danger imminent? Yes, danger of decreasing stability. (C)Is danger imminent? Yes, danger of breaking apart. (D)Is danger imminent? Yes, danger of environmental pollution.