Which of the Following Statements Is Not True

Which of the following statements is not true?

A) Many plants exhibit alternation between haploid and diploid stages.
B) Chromosome number is generally constant within groups of organisms with common ancestry.
C) The Y-bearing sex is known as the heterogametic sex.
D) Sex determination is chromosomal in some organisms and genic in others.
E) The sex chromosome systems of birds and mammals are likely to have evolved independently.