The correct answer is C) The same body can be used for a fix from observations separated by several minutes. The key advantage of high altitude observations is that the same celestial body (e.g. star, planet) can be used to obtain multiple sextant altitude measurements over a period of several minutes. This allows the navigator to establish a "fix" on the ship's position, using just one celestial body, by triangulating the position from these separated observations. This is a major advantage over low altitude observations, where the body's rapid movement would require using multiple different bodies to establish a fix. The other answer choices are incorrect because: A) Parallax is not eliminated at high altitudes, B) Declination is still required in the celestial navigation calculations, and D) The semidiameter correction is still necessary even at high altitudes.