Answer:
Harmful mutations may cause genetic disorders or cancer. A genetic disorder is a disease caused by a mutation in one or a few genes. A human example is cystic fibrosis. A mutation in a single gene causes the body to produce thick, sticky mucus that clogs the lungs and blocks ducts in digestive organs.
Mutations arise spontaneously at low frequency owing to the chemical instability of purine and pyrimidine bases and to errors during DNA replication. Natural exposure of an organism to certain environmental factors, such as ultraviolet light and chemical carcinogens (e.g., aflatoxin B1), also can cause mutations.
only a small percentage of mutations cause genetic disorders—most have no impact on health or development. For example, some mutations alter a gene's DNA sequence but do not change the function of the protein made by the gene.
Amongst the options given, the possible answer would be "that Sayuri's intelligence is way beyond her years". A critical person can arrive at this answer because the situation stated that Sayuri had habits that differ from other children. Those extraordinary habits can be connected to the child's intellectual level. Kids that are more intelligent than the others will tend to display habits that are out of the ordinary.
I believe "reasonable" would be the word you are looking for there.
