单项选择题 What will be the result of attempting to run the following program？（）   public class Qaa75 {   public static void main（String args[]） {   String[][][] arr = {   { {}， null }，   { { "1"， "2" }， { "1"， null， "3" } }，   {}，   { { "1"， null } }  }；   System.out.println（arr.length + arr[1][2].length）；   }   }

多项选择题 Which code fragments will succeed in initializing a two-dimensional array named tab with a size that will cause the expression tab[3][2] to access a valid element？（）   CODE FRAGMENT a：  int[][] tab = {  { 0， 0， 0 }，  { 0， 0， 0 }  }；   CODE FRAGMENT b：  int tab[][] = new int[4][]；  for （int i=0； i   CODE FRAGMENT c：  int tab[][] = {  0， 0， 0， 0，  0， 0， 0， 0，  0， 0， 0， 0，  0， 0， 0， 0  }；   CODE FRAGMENT d：  int tab[3][2]；   CODE FRAGMENT e：  int[] tab[] = { {0， 0， 0}， {0， 0， 0}， {0， 0， 0}， {0， 0， 0} }；

单项选择题 Itisdesirablethatacertainmethodwithinacertainclasscanonlybeaccessedbyclassesthataredefinedwithinthesamepackageastheclassofthemethod.Howcansuchrestrictionsbeenforced？（）