Read the passage from When Birds Get Flu and Cows Go Mad! by John DiConsiglio.

The human version of mad cow resembles a rare brain disease called variant Cruetzfeldt-Jakob disease (vCJD). It seems to affect mostly young adults. It strikes five or more years after the victim ate bad meat. In every case, the infected person has died.

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.

Which cause-and-effect signal words in the passage point to the result of a problem?

A) the human version
B) in every case
C) chances are
D) but, for reasons