Consider the following statements according to Werner's theory:
$1.$ Ligands are connected to the central metal ions by coordinate 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