The word “impairs” in line 1 is most similar to which of the following?
A.affects
B.destroys
C.enhances
D.diminishes

According to the passage, where is nerve growth factor produced in the body?
A.in nerve cells in the spinal column
B.in red blood cells in the circulatory system
C.in nerve cells in the brain
D.in the pituitary gland

Which of the following is closest in meaning to the word “doses”?
A.measures
B.pieces
C.injections
D.stipends

The passage most closely resembles which of the following patterns of organization?
A.chronological order
B.statement and illustration
C.cause - effect
D.alphabetical order

_________ (24)
A.mode
B.means
C.course
D.measure

_________ (25)
A.yet
B.despite
C.because
D.so

_________ (27)
A.estate
B.state
C.stage
D.position

_________ (28)
A.into
B.through
C.at
D.with

_________ (30)
A.discovery
B.revelation
C.detection
D.disclosure

What is the main topic of the passage?
A.A revolution in communication
B.The invention of optical fibers
C.New surgical techniques
D.The roles of optical fibers in medicine