Answer:it was very effective.
Explanation:
According to report in America 1954, Salk conducted a national study, with over a million paediatric subjects wish yielded a positive outcome and on 12 April 1955, the vaccine was considered safe and efficacious. in 1955, the vaccines was used for over 29,000 cases of poliomyelitis in the US and the infection rate reduced to less than 6,000. This made Salk vaccine more recognized and it was speedily adopted worldwide reaching almost 90 countries in less than 2 years after it mass production.
The most widely used renewable energy source is hydropower. While this has many benefits, it also causes many environmental concerns when the dams get built.
Answer:
In humans, each cell normally contains 23 pairs of chromosomes.
Explanation:
Answer:
i think system is correct
Explanation:
for example heart is an organ. it has muscle tissue .epithelial tissue . connective tissue nervous tissue