Question: Which of these is in the grass family, Mertensia or Cymbopogon?

Context paragraphs:
Cymbopogon: Cymbopogon, better known as lemongrass ( ; ), is a genus of Asian, African, Australian, and tropical island plants in the grass family.

Cymbopogon schoenanthus: Cymbopogon schoenanthus, camel grass, camel's hay, fever grass, geranium grass, or West Indian lemon grass is a herbal plant of Southern Asia and Northern Africa, with fragrant foliage.  It is often made into a common herbal tea

Cymbopogon flexuosus: Cymbopogon flexuosus, also called Cochin grass or Malabar grass, is a perennial grass native to India, Sri Lanka, Burma, and Thailand.  It is placed in the genus "Cymbopogon" (lemongrasses).

Cymbopogon commutatus: Cymbopogon commutatus, widely believed to be synonymous with Cymbopogon parkeri, is a perennial grass species, commonly known as Incense grass, Aromatic rush, Camel's hay, or Lemon grass.  Its range extends from South Asia to parts of Africa and Arabia.  Foliage has a sweet lemony odor when mashed.  It appeared on a 4 riyal Qatari stamp.  It is used for medicinal purposes in northeastern Arabia.

Mertensia: Mertensia is a genus of flowering plants in the family Boraginaceae.  They are perennial herbaceous plants with blue or sometimes white flowers that open from pink-tinged buds.  Such a change in flower color is common in Boraginaceae and is caused by an increase of pH in the flower tissue.  "Mertensia" is one of several plants that are commonly called "bluebell".  In spite of their common name, the flowers are usually salverform (trumpet-shaped) rather than campanulate (bell-shaped).

Cymbopogon citratus: Cymbopogon citratus, commonly known as lemon grass or oil grass, is a tropical plant from South Asia and Southeast Asia.

Cymbopogon proximus: Cymbopogon proximus is a member of the genus "Cymbopogon" (lemongrasses) in the grass family (Poaceae).

Cymbopogon elegans: Cymbopogon elegans is a grass species in the genus "Cymbopogon".

Cymbopogon nardus: Cymbopogon nardus, common name citronella grass, is a perennial of the Poaceae grass family, originating in tropical Asia.

Cymbopogon martinii: Cymbopogon martinii is a species of grass in the genus "Cymbopogon" (lemongrasses) native to India and Indochina, but widely cultivated in many places for its aromatic oil.  It is best known by the common name palmarosa ("palm rose") as it smells sweet and rose-like.  Other common names include Indian geranium, gingergrass, rosha, and rosha grass.

Supporting paragraphs: Mertensia Cymbopogon
Answer: Cymbopogon