1. Impossible to answer
   "an unanswerable argument"

See also: incontestable, incontestible

• genus Cistus
• genus Citellus
• genus Citharichthys
• genus Citroncirus
• genus Citrullus
• genus Citrus
• genus Cladonia
• genus Cladorhyncus
• genus Cladrastis
• genus Clangula
• genus Clathrus
• genus Claviceps
• genus Claytonia
• genus Cleistes
• genus Clematis
• genus Cleome
• genus Clethra
• genus Clethrionomys
• genus Clianthus
• genus Cliftonia
• genus Clinopodium
• genus Clintonia
• genus Clitocybe
• genus Clitoria
• genus Clostridium