关于表证的病位，下列说法错误的是（） ["肌表","皮毛","骨髓","肌腠"]
合同可以采取口头形式，也可以采取书面形式，下面所列哪些属于合同的书面形式？（） ["合同书","电报、电传、传真","电话","电子数据交换和电子邮件"]
（）will reduce the visibility. ["dust","sea water","land sand","wind"]
根据我国合同法的规定，下列哪些合同是无效合同？（） ["一方以欺诈、胁迫的手段订立的合同","恶意串通，损害国家、集体或者第三人的利益而订立的合同","以合法形式掩盖非法目的的合同","损害社会公共利益的合同"]
（）view of the fact，I wish to submit this report. ["In","On","To","For"]
单元的概念是什么？
