Question

A city introduced a new bus rapid transit system, and within a year traffic congestion in the city center fell by 30 percent. The transport minister concluded that the new bus system was responsible for reducing the congestion. Which of the following, if true, most weakens the minister's conclusion?

• A. The bus rapid transit system was used by thousands of commuters every day.
• B. The bus system was more expensive to build than the city had originally expected.
• C. Several neighbouring cities have also recently built bus rapid transit systems.
• D. During the same year, a large employer relocated its offices out of the city center, removing many daily commuters.

Hint:

Look for an option that offers a completely separate explanation for the drop in congestion, rather than one that just describes the bus system's popularity or cost.

Answer 1

The Correct Option is D

Step 1: Identify the hidden assumption behind the minister's conclusion: that no other factor besides the bus system could explain the drop in congestion.
Step 2: Test option A - high daily ridership is consistent with the bus system working well; it does not supply an alternative explanation, so it does not attack the assumption.
Step 3: Test option B - construction cost has nothing to do with what caused the congestion to fall, so it is irrelevant to the assumption.
Step 4: Test option C - other cities building similar systems does not change what happened to congestion in this particular city, so it does not attack the assumption.
Step 5: Test option D - a major employer relocating out of the city center and removing many daily commuters supplies exactly the missing alternative cause the hidden assumption denies exists, directly undermining the minister's conclusion.
Correct option: (4) During the same year, a large employer relocated its offices out of the city center, removing many daily commuters.