How many names are provided in the binomial nomenclature of an organism?

The statement,'Systematics is the study of the diversity of organisms and all their comparative and evolutionary relationships,' is attributed to:

Which one of the following statements is correct about biodiversity?

The binomial system of nomenclature for plants is effective from which date?

$Nicotiana$ $sylvestris$ flowers only during long days,while $N.$ $tobacum$ flowers only during short days. If raised in the laboratory under different photoperiods,they can be induced to flower at the same time and can be cross-fertilized to produce self-fertile offspring.
What is the best reason for considering $N.$ $sylvestris$ and $N.$ $tobacum$ to be separate species?

For which of the following is the study of taxonomy essential?