Of the scenarios below, which represents the occurrence of evolution at its smallest scale?

an individual organism begins as a single cell and develops into an adult, changing dramatically through a series of life stages. an adult human moves from near sea level to a city high in the andes mountains. her physiology changes to improve her performance in the thin atmosphere. a pesticide spray is heavily used on a particular farm. initially it kills 98% of the grasshoppers on contact. over several generations, the local grasshopper population becomes resistant to the pesticide through inheritance of resistance alleles. other nearby grasshopper populations do not change in any noticeable way. over many thousands of years, the beak shape of a bird species changes to exploit a new food source.