¿Cómo calificaría usted, un orden adecuado para escribir un texto de divulgación científica?

Keeps you from getting lung cancer from smoking

The question may be incomplete (there are not the possible answers), but according to the scenario, kaley and her coworkers could be in a humanitarian organization like red cross (in the us or in other countries). it's an organization which organizes health and safety services, disaster services, and blood donations.

Immunization is the introduction of a foreign substance to provoke  the immune response system.  immunizations are the same as vaccinations. it introduces foreign (but dead/ weakened) illnesses to train the body to fight against them. specific viruses and bacteria have specific antigens, antigens act sort of like name tags. these name tags the immune system recognize what's dangerous to the body and what's safe. 

I'd probably say d as you would try to reassure them that everything would be ok and that they won't come to any harm.