Read the following statements carefully and identify correct statements $w.r.t.$ Lichens:
$a.$ The association cannot tolerate air pollution,especially due to sulphur dioxide.
$b.$ Lichens are annuals and their growth is slow.
$c.$ The fungal partner mostly belongs to Ascomycetes.
$d.$ Soredia are most efficient means of asexual reproduction.
$e.$ Orchids seldom occur without this association.
$f.$ Foliose lichens are pioneers of succession in a water body.

• A
  $c, d, f$
• B
  $a, c, d, f$
• C
  $a, b, e$
• D
  $a, c, d$