Biodiversity is

The correct option is number and type of plants present on earth.

Explanation:
Biodiversity, in a broad biological context, refers to the variety and variability of life on Earth. According to the options provided and the designated correct choice, biodiversity is represented here by the variety (types) and abundance (number) of plant species—also known as flora—inhabiting the planet.

Plants form the foundational trophic level of terrestrial ecosystems, converting solar energy into chemical energy through photosynthesis and providing habitat and oxygen. Thus, mapping the diversity of these plant species is a fundamental aspect of understanding ecological biodiversity.