Perhaps the best news about mad cow is that people do not catch it easily. Chances are, millions of people have eaten infected beef. But, for reasons scientists still do not understand, only about 150 people have gotten vCJD and died from it.

The tone of the passage is

reassuring

Explanation:

The definition of the tone in literature is that it is a manner in which the author expresses his attitude towards the topic, the atnosphere he creates.

The particular tone can be achieved by means of choice of words, level of formality, syntax use, diction etc.

Here, we see that the author sound optimistic; he brings good news about the disease stating that the chance of catching it is astronomically low. This optimistic, comforting and encouraging type of writing gives this passage a reassuring tone.

she was trying to use   reliable narrator.

a caption indicating the purpose of the diagram

explanation: