Examples of vestigial structures include a. Human thumbs
b. Human eyes
c. Whale gills
d. None of the above

d.None of the above

Explanation:

Vestigial structures are anatomical feature or behavior that no longer seems to have a purpose in the current form of an organism of the given species. Often, these vestigial structures were organs that performed some important function in the organism at one point in the past. Which means these need to have an important function.

primary succession begins with a bare rock and ends with a forest secondary succession begins after a natural disaster where there is a temporary setback after a forest fire or local destruction, but the surrounding area can fill in

correct answer is a. and d.