(a(i))[3]
Calculate the percentage change in the number of polio cases from 1950 to 1952 in Fig. 6.1. Give your answer to two significant figures.
(a(ii))[5]
Explain how vaccination leads to the pattern shown between 1958 and 1970 in Fig. 6.1.
(a(iii))[2]
Explain why the polio vaccine does not protect you against other diseases.
(b)[3]
Outline how a blood clot forms and how it can stop infections.
(c)[1]
State the name of the blood component that carries blood cells.