中国大学MOOC: One of the key reasons why older mothers tend to give birth to babies with trisomies is:

One of the key reasons why older mothers tend to give birth to babies with trisomies is: A: Delayed stabilization of cohesins during meiosis. B: Premature degradation of cyclins during meiosis. C: Premature degradation of cohesins during meiosis. D: Premature resolvement of chiasmata during meiosis.