Which trait is unique to birds?

Flight
Wings
Endothermic
Feathers

answer; ///(b) it is composed of four protein chains and four heme groups;

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.

no i don't feel that humans have oversubscribed some medications

in the year 2850, humans successfully colonized mars. the martian modules that were constructed could hold only a small population of people. it is now a century later, and the population on mars has grown to 600 people. of the current mars population, 45 people express the recessive phenotype for phenylketon- uria (pku) syndrome (pp genotype).

explanation: