Which of the following is true for a $Subfamily$?

Assertion $A$: Linnaeus is known as the father of taxonomy.
Reason $R$: Linnaeus classified plants into $24$ groups based on floral characteristics.
Which option is correct for Assertion $A$ and Reason $R$?

$A :$ $A$ group of closely related families forms an order.
$R :$ The families of an order show close resemblance in certain fundamental features and also in evolutionary trends.

Brassica campestris Linn
$(a)$ Give the common name of the plant.
$(b)$ What do the first two parts of the name denote?
$(c)$ Why are they written in italics?
$(d)$ What is the meaning of Linn written at the end of the name?

What is the genus of the sunflower?

$A$ group of closely related species is known as.......