Thorn of Bougainvillea and tendril of Cucurbita are:

Homologous structures

The correct answer is Option (1) → Homologous structures

Homology is based on divergent evolution .Homology indicates common ancestry. They perform different functions but  have similar anatomical structure –examples are vertebrate hearts or brains. In plants also, the thorn and tendrils of Bougainvillea and Cucurbita represent homology. Whales, bats, Cheetah and human (all mammals) share similarities in the pattern of bones of forelimbs. Though these forelimbs perform different functions in these animals, they have similar anatomical structure – all of them have humerus, radius, ulna, carpals, metacarpals and phalanges in their forelimbs. Hence, in these animals, the same structure developed along different directions due to adaptations to different needs.