He need to tell the truth. you could not lie to them. because he need to fill up some forms which ask for questions like this. if you lie this time, and if US find out his lying, (it is possible for US to find out this, very easy), he would be no long to enter US in his life. rejecting his visa is no big deal for him, he could try again. but if he is lying, he would make a big trouble in his life.