Consider the following statements regarding Werner's theory of coordination compounds:
$(1)$ Ligands are connected to the metal ions by coordinate bonds (dative bonds).
$(2)$ Secondary valencies have directional properties.
$(3)$ Secondary valencies are non-ionisable.
Which of these statements are correct?

• A
  $1, 2$ and $3$ are correct
• B
  $2$ and $3$ are correct
• C
  $1$ and $3$ are correct
• D
  $1$ and $2$ are correct