I have initially chosen E, while the correct answer is C, but now I see the difference.
Because Halley’s comet changes orbit slightly during the seventy-six-year intervalbetween passing close to Earth, it may veer onto a collision course with a planet sometime in the distant future.
(C) between its passes - implies that the comet changes its orbit between times it passes close to Earth, which makes more sense. I.e. scientist have measured comet's orbit twice in 1900 and then in 1976 at times
...
Because Halley’s comet changes orbit slightly during the seventy-six-year intervalbetween passing close to Earth, it may veer onto a collision course with a planet sometime in the distant future.
(C) between its passes - implies that the comet changes its orbit between times it passes close to Earth, which makes more sense. I.e. scientist have measured comet's orbit twice in 1900 and then in 1976 at times
...
.jpg)
