Identify the correct sequence of events of pollen-pistil interaction given below.
$(a)$ Pollen tube grows through the stigma,style and reaches the ovule.
$(b)$ Pollen grain lands on the stigma.
$(c)$ Pollen germinates to form pollen tube.
$(d)$ Pollen tube carrying $2$ male gametes enters the ovule.
Choose the correct option.

• A
  $b \rightarrow c \rightarrow d \rightarrow a$
• B
  $b \rightarrow c \rightarrow a \rightarrow d$
• C
  $b \rightarrow a \rightarrow c \rightarrow d$
• D
  $b \rightarrow d \rightarrow a \rightarrow c$