Consider the following statements about methanogenic bacteria:
$I.$ Methanogenic bacteria are commonly found in the anaerobic sludge formed during sewage treatment.
$II.$ These bacteria also occur in the rumen of cattle,where they act upon cellulosic material to break down cellulose.
$III.$ They play a very important role in the nutrition of cattle by digesting cellulosic material.
Which of the statements given above are correct?

• A
  $I, II$ and $III$
• B
  $I$ and $II$
• C
  $I$ and $III$
• D
  $II$ and $III$