Unit 12 Reading 2

3. A puzzling question, person, or thing that is difficult to understand
6. To keep safe from harm, injury, or damage
8. A system of parts working together, or a process by which something takes place
10. Resistant to a particular infection, toxin, or penalty
11. The act of making a change or modification
17. Decided or established in advance
18. The quality of being new, original, or unusual
19. To completely remove or get rid of something
20. To a great or significant degree; considerably

1. To increase rapidly in numbers or multiply
2. To move from one region or habitat to another
4. Causing confusion, bewilderment, or difficulty in understanding
5. To escape or avoid someone or something, especially by cleverness
7. Required by law, rule, or authority; compulsory
9. The smallest structural and functional unit of an organism
12. To enter a place or situation where one is unwelcome or uninvited
13. To improve something by making small changes, or to remove impurities
14. To give all or a large part of one's time or resources to a cause or person
15. To insert or fix firmly into an area, tissue, or person's body
16. To make previously unknown or secret information known to others