There isn't any one food that contains *everything* we need to survive. However, it is possible to live one's entire adult life on a vegan diet without any animal products whatsoever. Soybeans contain all [22 ?] of the necessary amino acids... and many cultures live quite well on rice and corn, or, rice, lentils, garbanzo beans, etc.
My mum always said you could live on baked beans; fibre, protein, vitamin C, sugar, salt and water. I think she was just trying to convince me to stick out my degree!
And according to Kelloggs, you can live on cereal. No questionable marketing gimmick there eh.
I think the point of the questions, TracyH, is whether an adult human could survive on a particular food. Babies are a completely different matter. Do you think an adult human could survive for 8 months on breast milk? (..Anyone care to volunteer for the experiment??!)
My husband's grandmother was in the Leningrad blockade and all she had to eat was black bread. A lot of people starved to death that way but one village had only cabbage and they all were surprisingly healthy at the end of it.