Answer: 2. \(\textit{Mangifera indica}\) Linn.
Key idea: In a scientific name the genus starts with a capital letter, the species with a small letter, both italicised, and the author name follows in normal type, abbreviated.
Mango was described by Linnaeus, abbreviated as Linn. (author citation is written only once, as the name of the person, with no first name abbreviation such as "Car."). So Mangifera indica Linn. is correct. Option 4 has a capital in the species name; option 3 lacks the author; option 1 wrongly adds "Car.".