How many meiotic divisions are required to produce $100$ functional megaspores in angiosperms?

Which of the following organisms reproduces only once in its lifetime?

If a plant bears only staminate flowers, what is it called?

In . . . . . . ,pollen grains are long and ribbon-like.

Match the following columns:

Column-$I$ (Pre-fertilization)	Column-$II$ (Post-fertilization)
$P$. Ovule	$I$. Fruit
$Q$. Ovary	$II$. Seed
$R$. Integument	$III$. Seed coat
$S$. Ovary wall	$IV$. Pericarp

Rose plants produce large,attractive bisexual flowers but they seldom produce fruits. On the other hand,a tomato plant produces plenty of fruits though it has small flowers. Analyse the reasons for the failure of fruit formation in roses.