You Sample the Solid Waste of Three Infants from Three

Multiple Choice

You sample the solid waste of three infants from three different families each week for 24 weeks. You find that the gut bacteria population is dominated by one species for the first 12 weeks, and then shifts to another species. Which of the following might be a major factor in this change?

A) The infants begin sleeping for stretches of 6 hours about 10 weeks into the sampling period.
B) The infants begin to smile about 8 weeks into the sampling period.
C) The infants begin eating solid food 24 weeks into the sampling period.
D) The infants begin to roll over 16 weeks into the sampling period.
E) None of answers are likely to be major factors in the gut bacteria population change described above.