Which of these plants is not poisonous?

"Pennisetum purpureum", also known as Napier grass, elephant grass or Uganda grass, is a species of perennial tropical grass native to the African grasslands. It has low water and nutrient requirements, and therefore can make use of otherwise uncultivated lands. In addition to this, Napier grasses improve soil fertility, and protect arid land from soil erosion. It is also utilized for firebreaks, windbreaks, in paper pulp production and most recently to produce bio-oil, biogas and charcoal.

Napier grass is the most important fodder crop for the dairy farmers in East Africa. Its high productivity makes it particularly suited to feed cattle and buffaloes. It is also an important forage for elephants in Africa, hence its name "elephant grass"

Atropa belladonna, commonly known as belladonna or deadly nightshade, is a drug perennial herbaceous plant in the nightshade family Solanaceae, which includes tomatoes, potatoes, and eggplant (aubergine). The foliage and berries are extremely toxic when ingested, containing tropane alkaloids.

Conium maculatum, the hemlock or poison hemlock, is a highly poisonous biennial herbaceous flowering plant in the carrot family Apiaceae, native to Europe and North Africa.

Castor oil plant is a common self-sown weed with toxic seeds, flowers and leaves. Chewing and swallowing a few seeds can cause severe nausea, vomiting, diarrhoea and abdominal pain.