Answer:
The ability to rapidly reproduce HeLa cells in a laboratory setting has led to many important breakthroughs in biomedical research. For example, by 1954, Jonas Salk was using HeLa cells in his research to develop the polio vaccine.
Explanation:
I believe that the answer is 2) trains, but if you are allowed to have multiple answers I would say put 1) trucks and 2) trains
OPTION C IS YOUR ANSWER
Italy and Germany were finally unified and they agueably the most nationalistic nations of the early mid 1900
