Answer: The right answer here is option (1) Reptiles and birds.
Evolution is kind of a process where changes are happening over the generations. The connecting link animals are those who belong to the two types of classes. For example, The archaeopteryx mainly shares the bird and the reptile link. It has wings, a beak, the particular structure of legs just like the birds, and on the other hand, it has reptile-like teeth and a tail. It also has reptile-like skin. So, you can say that it has evolved from a bird to a reptile. So, they are an example of connecting links. For this reason, option (1) is correct.