Which toxicity can result in slow growth and iron-deficiency anemia, and can damage the brain and central nervous system?
a. lead
b. iron
c. calcium
d. sulfur

The toxic that can cause slow growth and iron deficiency anemia that damages the brain and central nervous system is letter A - LEAD.
Lead could cause decrease in alertness level, slow mental function and mostly attention decrease. Lead is an unhealthy substance that could cause such diseases.

Blood transfusions were rarely done and often fatal; they were outlawed until the nineteenth century.