The correct option is C Cocos nucifera
All scientific names have to have two names, the first is the generic name and the second is the specific name.
The genus begins with a capital letter and the species begins with a small letter. When the scientific name is typed or printed, it should be in italics and when handwritten, it should be underlined.
Hence, Cocos nucifera is the correct form of writting scientific name using the rules of Binomial Nomenclature.