Answer with explaining the reason behind option.

Discoidal cleavage is generally found in the eggs of birds, reptiles and fish. In this type of cleavage, furrow do not penetrate the yolk.

Ans 18. Rapid mitotic division
​​​​​​The term cleavage refers to the series of rapid mitotic divisions of zygote following the fertilization which forms several-celled blastula. 

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