Analysis of air bubbles trapped in fossils, such as in fossil amber, show that our air in earliest times contained about 35% oxygen. Today, the average oxygen content of our air is approximately 20%. In some larger, more polluted cities, oxygen content in the air has been measured at 12 - 15%.
There are 297 words which start with 'pen'. 3 letter words starting with 'pen': pen. 4 letter words starting with 'pen': pend. pens.
Hang On and Weigh In! The Latin root word pend means âhang,â and its variant pens means âhangâ or most often âweigh.â. When you are de pend ent upon another person, for example, you âhangâ from him. Of course, when you are completely inde pend ent, you do not âhangâ from anyone or anything!