单选题 Were animal parents judged by human standards, the cuckoo would be one of nature"s______ creatures, blithely laying its eggs in the nests of other birds, and leaving the incubating and nurturing to them.
【正确答案】 D
【答案解析】解析：句意：如果按人类的标准来评判动物亲代的话，杜鹃无疑是自然界中比较缺乏责任心的一种动物，它们漫不经心地将蛋产于其他鸟类的巢内，并将孵化和喂养的任务留给它们。mettlesome“精神抖擞的，有生气的”；industrious“勤奋的”；conscientious“认真的，尽责的”；feckless“无效的，不负责任的”。根据句意，D为答案。