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.
See if you can think of and write eight words that start with V in eight categories: a person's name, an animal, a food, an astronomy word, a verb (action word), something from the sea, a plant, and a place. Illustrate the words if you can. Sample answers: Velma, vulture, veal, Venus, vote, viper fish, vine, Vermont.