Need drop down options to insert different paragraphs within document

That is what will happen.  However, I would suggest that when creating the AutoText Entries, you DO create a new Category to use for each of the AutoText Entries that you create so that you can restrict the items that can be selected via the Building Block Gallery Content Control to just those AutoText Entries that you want the user to be able to select.

If you define a new category, such as MyForm in the following example when you create the first AutoText Entry and then assign that category to the second one as well, then when you insert the Building Block Gallery Content Control and access its Properties, select the AutoText Gallery and the MyForm Category as shown below.

Having done that, when you click on the Content Control drop down in the document, you will see

and when you choose an item OptionA or OptionB, (which were the names I used for the AutoText Entries), the Content Control will be populated with the contents of the selected option.

See Doug's reply.  However, if you must have a dropdown then without a whole lot of additional complicated code you will have to settle for the text to appear on the Exit from the CC.  This is because CCs don't have a change event:

Lets assume that you have a template with two building blocks defined in the AutoText gallery/general category. The first is named P1 and the second named P2.  In the template that contains the BBs, add this code to the "ThisDocument" module:

Private Sub Document_ContentControlOnExit(ByVal CC As ContentControl, Cancel As Boolean)
Dim oTmp As Template
Set oTmp = ThisDocument.AttachedTemplate
  Select Case CC.Title
    Case "DDPars"
      Select Case CC.Range.Text
        Case "A"
          CC.Type = wdContentControlText
          oTmp.BuildingBlockTypes(wdTypeAutoText).Categories("General").BuildingBlocks("P1").Insert CC.Range
          CC.Type = wdContentControlDropdownList
        Case "B"
          CC.Type = wdContentControlText
          oTmp.BuildingBlockTypes(wdTypeAutoText).Categories("General").BuildingBlocks("P2").Insert CC.Range
          CC.Type = wdContentControlDropdownList
        Case Else
      End Select
  End Select
End Sub

In the document add a dropdown CC with two list entries "A" and "B".  Title it DDPars