张洁，16岁。一天，她到某体育器材公司以9000元购买了一部美国原装高级跑步机，她父母认为她尚未成年，没有征得家长同意，不能进行大数额的买卖，要求公司退款。而张洁提出她是做临时工、自食其力的青年，不愿退货。
张洁的买卖行为是否有效
参考答案：因为张洁已年满16岁，并以自己工资收入作为主要生活来源，可以视为完全民事行为能力人，因而该买卖行为合法有效。
解析：参见《民法通则》第11条：“十八周岁以上的公民是成年人，具有完全民事行为能力，可以独立进行民事活动，是完全民事行为能力人。 十六周岁以上不满十八周岁的公民，以自己的劳动收入为主要生活来源的，视为完全民事行为能力人。”
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