In crop improvement programmes, virus-free clones can be obtained through
a)	Grafting	b)	Hybridization	c)	Embryo culture	d)	Shoot apex culture

(d)

Tissue culture technique can be utilized for the production of virus-free plants either by meristem culture chemotherapy or selective chemotherapy of larger explants from donor plants. Shoot apex consists of meristematic-cells, thus shoot apex culture is successful to obtain virus-free clones in crop improvement programmes