Answer:
it was only 90 percent effective
Explanation:
In 1954 a massive controlled field trial was launched, sponsored by the National Foundation for Infantile Paralysis. Almost two million U.S. children between the ages of six and nine participated. In some areas of the country half of these “Polio Pioneers” received the vaccine, while half received a placebo. In other areas of the country children who did not receive any vaccine were carefully observed. On April 12, 1955, Thomas Francis, Salk’s mentor and the director of the trial, reported that the vaccine was safe, potent, and 90% effective in protecting against paralytic poliomyelitis.
Answer:
Nitrogen fixing bacteria is the organism which is responsible for the fixing of atmospheric nitrogen into usable form for the plant.
Explanation:
Nitrogen fixing bacteria is a type of bacteria which fixes atmospheric nitrogen into ammonium and nitrates form. Plants are unable to take atmospheric nitrogen so it must be converted into available form i. e. nitrates and ammonium. Examples of nitrogen fixing bacteria are Cyanobacteria and Azotobactor etc. These nitrogen fixing bacteria lives in the root of the plant and makes symbiotic association.
Answer:
Low pH
Explanation:
The skin has sebaceous glands that secrete sebum. Sebum makes a protective layer over the surface of the skin and imparts it an acidic pH due to the presence of fatty acids in it.
Mostly, the pH level of skin is maintained within the range of 3-5 (acidic) which in turn serves as one of the barriers against pathogen provided by skin. Likewise, sweat glands of skin secrete sweat which also imparts the acidic pH to the skin to prevent any infection.
The answer is C, plate movement has no effect on climate change
Answer: B. when sunlight is absorbed in chlorophyll
Explanation:
