1 The main idea of the passage is .
a. how magnetic fields are used in everyday life
b. how an electromagnetic field works
c. how metal detectors and scanners work
d. how technology is helpful for our modern life
2. What is the fourth paragraph about?
a. The advantages of small X-ray scanners
b. How useful CT scanning technology is
c. How poor airport security is in many airports
d. How busy airports scan large amounts of baggage