Correct option (c) hybridisation
Explanation :
The common wheat is hexaploid with 2n = 42 and is derived from three diploid species :
(i) AA = Triticum monococcum (2n = 14 ),
(ii) BB = Aegilops speltoides (2n = 14),
(iii) DD = Aegilops squarrosa
The hexaploid wheat therefore, is designated as AABBDD, the tetraploid (2n = 28) as AABB and diploid (2n = 14) as DD. Thus, it is obtained from hybridisation.