Answer:
The correct answer is b. He determined that DNA contains four nitrogenous bases.
Explanation:
Levene was an American biochemist who studied the structure of DNA in the early 1900s and in 1920 he found that DNA consists of four nitrogenous bases that are Adenine, Guanine, Thymine, Cytosine.
He also found deoxyribose sugar and phosphate group and said that nucleotide is the basic unit of DNA which contains a ribose sugar with attached nitrogenous base and phosphate group.
He also concludes that an equal amount of adenine, guanine, thymine, and cytosine makes the DNA which is now known as tetranucleotide hypothesis. So the correct answer is b. He determined that DNA contains four nitrogenous bases.
Nervous tissue is made up of neurons and supportive cells. Throughout the human body the neurons carry electrical and chemical signals, while nutrition is provided by the supportive cells.
Oxygen and carbon dioxide is exchanged by the millions of alveoli in the lungs and the capillaries that envelop them. we inhale oxygen (which is then exchanged with carbon dioxide in the lungs) and then we exhale the carbon dioxide. although, the air that we breathe usually consists more nitrogen than oxygen.
1. The bottle left in the sun is exposed to the thermal energy which causes it to heat up. Ice is cold and the bottle is in direct contact with the ice.
2. Its harder for cold winds to get through to you when theres 3 or even 4 layers of clothing on your body than one thick one.
3. Common Sense?... the rug is thick and the tile is... a tile
