Thanks to its remote location and ________ terrain, Henderson Island has never been successfully colonised, either by people or by other introduced species.
句意： 由于地理位置偏远， 地形闭塞， 亨德森岛从未被人类或其他外来物种成功殖民过。
constraining约束的。 forbidding令人生畏的； 严峻的。 straining极度紧张的； 忍耐到极限的。 prohibit禁止。