The answer is D. Passive Acquired Immunity. I am 100% certain this is the correct answer.
C- Circulation
A- Airway
B- Breathing
1) Wrestling.
Explanation: Wrestling has been around for millions of years, Wrestling is something that comes along almsot everyday. Kid's wrestle(play fight), adults do too. Which makes it common. Also wrestling has been around for over 15,000 years!
2) Running.
Explanation: Running is very common, we all run daily which makes running common. Also running has been around for millions of years. Even dinosaurs ran. So that being said, running is one of the oldest competitive sports.
Both of these are both very competitive. either to win money or take home a trophy.
Millions of people compete for a title. Which makes them competitive.
Muscle tissue unless it's called something different In your book
