Why is your skin considered to be an organ

Which group of chordates does  notpossess true backbones?                 a.  birds      b.  frogs and toads      c.  lampreys      d.  crocodilians

Last week i was assigned a thematic. we have groups of three but the people i was assigned with haven't been in school for days. i would appreciate if anyone can me with my thematic . i highlighted most of the important steps and i circled my thematic topic. in desperate need : ( its due on february 19

In the presence of oxygen, glycolysis is followed a. the krebs cycle b. lactic acid fermentation c. alcoholic fermentation d. photosynthesis