Humanity is susceptible to many diseases. Some are endemic (always present in a population), and some sweep rapidly through widespread populations as epidemics. Only in the last century or so — when diseases were well-enough understood by science — have large-scale disease-eradication programs been implemented.According to the passage, endemic diseases are

When you’re answering the Paragraph Comprehension questions, keep these tips in mind:   
- Skim the passage and read the question. Then go back to the passage to find the answer. 
- Select the correct answer based on the passage rather than your personal knowledge or opinion on the subject.  
- Answer choices that include the word all, none, always, never, or some other absolute are rarely correct, so think twice before you settle on one of these answers.