Cristina and Juan are twins who developed from two separate fertilized ova that were fertilized by two different sperm, while Mary-Kate and Ashley are twins who developed from one fertilized ovum that was fertilized by one sperm. Cristina and Juan are twins, whereas Mary-Kate and Ashley are twins.

i- fraternal or dyzygotic twins

ii- monozygotic twins

Explanation: dyzygotic twins develop when two separate oocyte are fertilised by two different spermatozoa. They are also referred to as nonidentical or fraternal twins. They can be of the same or different sex.

Monozygotic twins develop when one oocyte fuses with one spermatozoa and splits into two after fertilization. These twins are also known as identical twins as they will be of the same sex and have the same gene, blood groups and physical features. They may be of different sizes and often have very different personalities and characters.

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