Question

question 8
a firefly uses specialized muscles to draw oxygen into its lower abdomen through narrow tubes, triggering a chemical reaction whereby the oxygen combines with chemicals in the fireflys abdomen to produce a glow. ______ when the firefly stops drawing in oxygen, the reaction—and the glow—cease.
which choice completes the text with the most logical transition?
a) for instance.
b) by contrast.
c) specifically.
d) in conclusion.

Explanation:

The first part describes the process when oxygen is drawn in for the glow - producing reaction. The second part describes what happens when oxygen intake stops. These are contrasting situations. "By contrast" is used to show such a contrast. "For instance" and "specifically" are used for examples or details, and "in conclusion" is for summarizing.

Answer:

B. By contrast