Bird skeletons are very delicate, and therefore, difficult to be preserved. The bones of the birds are soft. The small animals are very prone to physicochemical as well as biological decay. This is why the fossil record of bird is incomplete and well-preserved fossils of birds are rare to find, except at a few unusual sites.
Answer:
you....your not asking anything?
Liquid 1 and 4, because they have the same melting point and density.
To view space and the foreign objects scientist may find. Also for learning purposes because it financially cost a lot to send scientists to space for research. So for research purposes.
