Answer: C
Explanation:
LD50 is a measure of toxicity in animals. A chemical with a smaller LD50 is more toxic and in this question, Shiga toxin has a lower LD50, thus it is more lethal.
Allan already had a heart attack and can try to prevent another one by changing the diet, exercising, or even quit smoking, but there are non-modifiable risks such as age, sex and generic heritage, so If Allan is over 40 years old, male or comes from a family with heart diseases, Allan needs to be extra careful because those factors cannot be changed no matter how the way of life is changed.
