Adventitious roots are adventitious in their

Some roots, known as adventitious roots, develop from an organ other than the root, most commonly a stem or a leaf. They're especially abundant on underground stems like rhizomes, corms, and tubers, making it possible to replicate many plants vegetatively from stem or leaf cuttings.

Adventitious roots are plant roots that grow from non-root tissue and are formed both during normal development and in response to environmental factors. Hence the correct answer is option C, place of origin.