It has been well documented that women above 40 have an increasing chance of giving birth to babies with Down syndrome. Why is this so?

A) Egg development starts at the fetal stage of women.
B) Eggs are in meiosis I at that time of fertilization.
C) The egg doesn't complete division (meiosis II) until fertilization.
D) The cellular machinery is unable to separate the chromosomes and chromatids, resulting in gametes with abnormal chromosome numbers.
E) All the above are true.