向量组<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/3b9f3d68443841c28d449945ec603530.png?x-oss-process=image/sharpen,200"/>,<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/3fecce37da044b0b8ef6f3776a484d2b.png?x-oss-process=image/sharpen,200"/>,<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/2fb68fefb9ca4d219dbe56257c2fa44a.png?x-oss-process=image/sharpen,200"/>,<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/c342b999a3034258bee77487ead2a5a4.png?x-oss-process=image/sharpen,200"/>的最大无关组为( )