The production of offspring in human by sexual reproduction includes the fusion of two gametes which are

$A$ - In several fungi and plants terms such as Homothalic.

$R$ - Dioecious are the terms used to describe unisexual condition.

Identify $X$ and $Y$ in given figure

........and..........is example showing external fertilization

Juvenile and adult plants are

$A$ -In Plant, the end of juvenile phase which makes the : beginning of the growth phase.

$R$ -In Plant, Juvenile phase is also known as vegetative phase.