16Hit1600
Expression of IdeasVery hardRhetorical synthesis: matching content to a specified audience

Expression of Ideas practice question

While researching a topic, a student has taken the following notes: • Muography is an imaging technique that uses muons—subatomic particles produced when cosmic rays strike Earth's atmosphere. • Muons travel through solid rock, but denser rock absorbs more of them than less dense rock does. • Physicist Hiroyuki Tanaka and his colleagues applied muography to Sakurajima, an active volcano in Japan. • The team installed detectors on the volcano's flank and counted the muons arriving from many different directions over several months. • Comparing the counts direction by direction allowed the team to map density differences inside the volcano. • The resulting maps revealed a low-density channel, which the team identified as the conduit that carries magma toward the summit.

The student wants to describe the team's procedure to an audience that is already familiar with muography. Which choice most effectively uses relevant information from the notes to accomplish this goal?

  1. A. Muography is an imaging technique that relies on muons, subatomic particles produced when cosmic rays strike Earth's atmosphere.
  2. B. Because denser rock absorbs more muons than less dense rock does, muons can be used to detect density differences deep inside a volcano.
  3. C. Installing detectors on Sakurajima's flank, the team counted the muons arriving from many different directions over several months and compared those counts to map density differences inside the volcano.Correct
  4. D. Tanaka and his colleagues' maps of Sakurajima's interior revealed a low-density channel, which the team identified as the conduit that carries magma toward the summit.

Answer: C. Installing detectors on Sakurajima's flank, the team counted the muons arriving from many different directions over several months and compared those counts to map density differences inside the volcano.

Two constraints must both be satisfied: describe the PROCEDURE, and address an audience that already knows what muography is. Only C reports what the team actually did (installed detectors, counted muons by direction over months, compared counts). (A) defines muography — information the specified audience already has, so it fails the audience constraint and reports no procedure. (B) states the underlying physical principle, again already known to this audience, and describes what muons can do in general rather than what this team did. (D) reports findings, not method — the common error of confusing results with procedure.

Why the other answers are wrong

A. Muography is an imaging technique that relies on muons, subatomic particles produced when cosmic rays strike Earth's atmosphere.
This defines muography, which your audience already knows, and it describes no step the team took.
B. Because denser rock absorbs more muons than less dense rock does, muons can be used to detect density differences deep inside a volcano.
This states the physical principle behind the technique — again already familiar to this audience — and describes what muons can do in general, not what Tanaka's team did.
D. Tanaka and his colleagues' maps of Sakurajima's interior revealed a low-density channel, which the team identified as the conduit that carries magma toward the summit.
This reports the team's findings (the low-density magma conduit) rather than the procedure that produced them.

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