The correct option is C To ensure fertilisation of at least few of them
The number of eggs produced by a species depends on the chances of fertilisation and level of parental care. In fishes and frogs, the eggs get exposed to water movement, wind and rainfall. The chance of fertilisation of the egg increases if a large number of sperms are released. However, in hens, the fertilisation is internal, with higher chances of fertilisation. Therefore, hens lay only one egg at a time.