Option 1 (I and II): This option suggests that both the pairs Crocodile - Reptile and Frog - Amphibian are incorrect. However, this is not true. Crocodile is indeed a reptile and frog is indeed an amphibian. Therefore, option 1 is not the correct answer.

Option 2 (I and III): This option suggests that both the pairs Crocodile - Reptile and Tiger - Reptile are incorrect. The pair Crocodile - Reptile is correct, as mentioned earlier. However, the pair Tiger - Reptile is incorrect. Tigers are not reptiles; they are mammals. Therefore, option 2 is the correct answer.

Option 3 (Only III): This option suggests that only the pair Tiger - Reptile is incorrect. This is the correct answer, as explained above.

Option 4 (Only II): This option suggests that only the pair Frog - Amphibian is incorrect. This is not true, as mentioned earlier. Therefore, option 4 is not the correct answer.

Therefore, the correct answer is option 3.