Which of these is an example of gradualism?

Question

1 the variation of tortoise shells that evolved as tortoises lived on different islands with different habitats

2 slow evolution of whales from a four legged land mammal over millions of years

3 rapid speciation following a catastrophic event

4 separate evolution of flight in birds and bats

Answer 1

2 slow evolution of whales from a four legged land mammal over millions of years