Answer:
a. Diet may be the cause of beriberi, but more research is needed.
Step-by-step explanation:
As you can see in the question above, when the hens' diets were changed, they no longer showed signs similar to those caused by beriberi. Which means that there may be a relationship between the incidence of beriberi and food. However, this result may be just a coincidence, or it may not occur in humans in the same way that it occurs in chickens, which leads to the need for more scientific research carried out to test the relationship between the incidence of beriberi and the food of humans.
These researches have already been carried out and currently, it is already known that beriberi is indeed related to vitamin B1 deficient food.