Complete the following sentence with a (compound) word derived from the one(s) given in bracket.
No snake known（ ）will attack human beings unless its life is threatened. (habitual)
【正确答案】：HABITUALLY
【题目解析】：
本题考查副词。
分析语境，已知的蛇中还没有...攻击人类的，...。这里需要一个副词修饰attack。因此答案为habitually。
句意：没有已知的蛇习惯性地攻击人类，除非它的生命受到威胁。