Answer: Solar energy
Explanation: That's what I would put.
Brain is protected by skull,blood brain barrier for filtration,cerebrospinal fluids that cushion brain and three membranes called duraarchnoid and pia mater
This was a hard one but I did some research and I found this
Our genome has 3 billion base pairs so a naive calculation shows 3x10^36 different combinations. But that's a meaningless number. A lot of those variants would be silent mutations, i.e. changes in introns, repeated sequences, 3rd position codons, etc etc that would have no effect on the phenotype.
Hope this help
