they---here once in the past .a,came b,have come .c has come 答案是过去式,不可以选b吗

they---here once in the past .a,came b,have come .c has come 答案是过去式,不可以选b吗
they---here once in the past .a,came b,have come .c has come 答案是过去式,不可以选b吗

they---here once in the past .a,came b,have come .c has come 答案是过去式,不可以选b吗
现在完成时表示过去发生并且已经完成的动作对现在造成影响或后果,过去某一时间开始并一直持续到现在并且有可能还会持续的动作或状态,本句结尾有in the past ,只是说他们过去来过一次,与现在无关