#define D_Question (2342)

ShowPlayerDialog(playerid, D_Question, DIALOG_STYLE_LIST,
 "Who is the current president of the USA?", "\
  Bush\r\n\
  Obama\r\n\
  Clinton", "Ok", "Cancel");

public OnDialogResponse(playerid, dialogid, response, listitem, inputtext[])
{
    if(dialogid == D_Question)
    {
        if(!response)
            return ShowPlayerDialog(playerid, D_Question, DIALOG_STYLE_LIST, "Who is the current president of the USA?", "Bush\r\nObama\r\nClinton", "Ok", "Cancel");
        if(listitem == 2) //not sure if this is 2 or 1 - correct me if the list starts with 0 not with 1
        { //correct answer
        }
        return 1;
    }
    return 0;
}