The correct option is C Companion cells
Phloem is the vascular tissue responsible for transport of sugars and other liquid materials. Phloem is composed of several cell types including sclerenchyma, parenchyma, sieve elements and companion cells. The function of companion cells is uncertain though it appears to regulate the activity of the adjacent sieve elements. Albuminous cells have a similar role to companion cells, but are associated with sieve cells only and are, hence, found in gymnosperms.