Select the incorrect statement among the following. (1) p² + 2pq + q² = 1 is binomial expansion of (p + q)². (2) When frequency measured differs from expected values, the difference indicates the extent of evolutionary change. (3) Hardy-Weinberg principle says that phenotype frequencies in a population are stable and constant from generation to generation. (4) The gene pool remains a constant; sum total of all the allelic frequencies is