Answer:
Jonas Salk was awarded the Nobel Prize for discovering a way to vaccinate against polio in the United States in the 1950's. This allowed millions of school-age children to avoid crippling disease, and to swim during summer again, as polio was often spread in public swimming areas before.
The statement that best describes how the polio vaccine works is:
It triggers the immune system to produce antobodies to fight the disease-causing agent.
Explanation:
There are two main reasons for this answer. The first one is that every vaccine is aimed to introduce a controlled amount of antigenes to be accepted by the organism. These antigens are made after some studies were conducted in a lab and were obtained from substances that the human body can accept to train the immune system to develop an effective defense for the virus or bacteria on the matter. In our case, the polio vaccine works the same way and allowed to save many lives.
The statement which explains why muscle cells and skin cells do not look and act the same is this: THE GENES IN EACH TYPE OF CELL ARE BEEN EXPRESSED DIFFERENTLY.
All the cells in human's body has the same set of genes, this is because, all the cells in the body originated from a single fertilized egg. Even though all the cells in the body has the same origin, they are different from one another because, the cells use the same set of genes differently.
The correct answer is C) 70/x.
To calculate doubling time, rule of 70 formula is used. For this the annual growth rate of the population is required. In this question growth rate is given x. Thus, doubling time = 70/ growth rate.
Therefore, doubling time = 70/x.
