Complete the following sentence with a (compound) word derived from the one given in bracket.
She could not give us a （ ） explanation for her decision to give up the opportunity. (reason)
【正确答案】：REASONABLE
【题目解析】：
空格前有冠词a，后有名词explanation，可知应填形容词，reason的形容词形式为reasonable。句意：她不能给我们一个合理的解释，说明她放弃这个机会的决定。