Which of these is a complete stem parasite?

Answer: Option B

Cuscuta is a complete stem parasite.
Cuscuta commonly known as dodder or amarbel, is a genus of over 201 species of yellow, orange, or red (rarely green) parasitic plants.
It is an ectoparasite and is categorized as a holoparasitic plant or a plant that is non-photosynthetic and is completely dependent on a host. The dodder can grow and attach itself to multiple plants. In tropical areas, it can grow more or less continuously and may reach high into the canopy of shrubs and trees.