第22题: [单项选择]Although the hazards of space travel are many, tile rewards made it a worthwhile ______. A. endeavor B. execution C. expenditure D. expedition 参考答案:A 答案解析:[解析] 逻辑关系题:解释。[A]endeavor“努力,尽力”是对space travel的描述,space travel是一种努力。[B]execution“执行,执行”;[C]expenditu