A species of bird has not been seen since the 1900s and is considered extinct. Which evidence would best disprove the claim that the bird is extinct?

Possible answers:
(a). A bird watcher makes a sketch of the bird.
(b). A scientist discovers fossil remains of the bird.
(c). A researcher takes a photograph of the bird.
(d). A park ranger finds a suitable habitat for the bird.
(c).