下列sql语句运行结果是： B select lpad('wjg',3,'-') from dual; select lpad('wjg',2) from dual; select rpad('wjg',5,'-') from dual; select rpad('wjg',2) from dual; A wjg; wj; wjg--; jg; B wjg; wj; wjg--; wj; C ---; wj; wjg--; wj; D ---; wj; wjg--; jg;