明清统治者实行“海禁”政策的出发点是
A.避免西方经济侵略
B.巩固自然经济基础
C.稳定国内统治秩序
D.缓和中外民族矛盾
答案:C
x2+5x+1=0.
import java.io.* ; public class abc public static void main(String args[ ]) ) System.out.println("a="+a+"\nb="+b); class SubClass extends SuperClass int c;SubClass(int aa,int bb,int cc) super(aa,bb); c=cc; class SubSubClass extends SubClassint a;SubSubClass(int aa,int bb,int cc) super(aa,bb,cc); a=aa+bb+cc;void show() System.out.println("a="+a+"\nb="+b+"\nc="+c);