The correct way to write the botanical name of a pea plant is ______.

The correct option is B Pisum sativum
The botanical name of a pea plant is Pisum sativum. A scientific name should be written following the binomial nomenclature rules. Genus name should begin with a capital letter, followed by species name in small letters. Also, when printed or typed, it should be in italics.

So, the correct answer is option B.