Non-disjunction can be caused by

The correct option is C Failure of chromosomes to separate during meiosis
Non-disjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division. It results in daughter cells with abnormal chromosome numbers. Calvin Bridges and Thomas Hunt Morgan discovered the process of nondisjunction in dividing cells in the year 1910. This is one of the most common forms of chromosomal aberration that occurs in humans.

So, the correct option is 'Failure of chromosomes to separate during meiosis'.