(21)下面正确使用动态数组的是
  A)Dim arr() As Integer
  …
  ReDim arr(3,5)
  B)Dim arr() As Integer
  …
  ReDim arr(50)As String
  C)Dim arr()
  …
  ReDim arr(50) As Integer
  D)Dim arr(50) As Integer
  …
  ReDim arr(20)
  (22)下面是求最大公约数的函数的首部
  Function gcd(ByVal x As Integer, ByVal y As Integer) As Integer
  若要输出8、12、16这3个数的最大公约数,下面正确的语句是
  A)Print gcd(8,12),gcd(12,16),gcd(16,8)
  B)Print gcd(8,12,16)
  C)Print gcd(8),gcd(12),gcd(16)
  D)Print gcd(8,gcd(12,16))
  (23)有下面的程序段,其功能是按图1所示的规律输出数据
  Dim a(3,5) As Integer
  For i=1 To 3
  For j=1 To 5
  A(i,j)=i+j
  Print a(i,j);
  Next
  Print
  Next
  
  若要按图2所示的规律继续输出数据,则接在上述程序段后面的程序段应该是
  A)For i=1 To 5
  For j=1 To 3
  Print a(j,i);
  Next
  Print
  Next
  B)For i=1 To 3
  For j=1 To 5
  Print a(j,i);
  Next
  Print
  Next
  C)For j=1 To 5
  For i=1 To 3
  Print a(j,i);
  Next
  Print
  Next
  D)For i=1 To 5
  For j=1 To 3
  Print a(i,j);
  Next
  Print
  Next