After penetrating stigmatic and styler tissues, the pollen tube usually grow down towards the egg because

What is correct for parthenium (Carrot grass)?

$(a)$ It came into India as a contaminant with imported wheat

$(b)$ It causes allergy

$(c)$ Asexual reproduction occurs in its flower

$A$ – Only some cells of the sporogenous tissue is capable of giving rise to microspore tetrad.

$R$- The microspores are arranged in a cluster of four cells – the microscopic tetrad.

Examine the figure given below and select the right option giving all the four parts $a, b, c$ and $d.$ Correctly identify

$a\quad \;b\quad\;c\quad\;d$