Litchi is commercially propagated by

Answer: Option C

Litchi is commercially propagated by Air layering.
Air-layering or 'Gootee' is a widely accepted method of propagation in India. In this method, a healthy and vigorous, upright twig of about one year old and 2.5 to 4 cm in diameter is selected. A circular strip of bark about 2 cm wide just below a bud is completely removed from the selected twig.
The most commonly used commercial method of propagation of litchi is air layering. Litchis can also be propagated by seeds, grafting or cuttings. The highly heterozygotic characteristic of this species prevents the commercial propagation by seeds.