A modifier question tests whether you can connect an opening describing phrase to the right noun. When that phrase tells what someone has done, ask who did it and use the passage to name them. An opening describing phrase must describe the main noun right after its comma, so predict that noun first. Then check the start of each completion and read it through the period. A name elsewhere in the sentence doesn’t change which noun the phrase describes.
Hints
- Hint 1
Look at the phrase beginning Having held and ask who kept the two conditions fixed. Use the first sentence to connect it to whoever ran the test.
- Hint 2
Find the main noun right after the opening phrase’s comma. The opening phrase describes that noun, so read them together and check who is being credited with keeping the conditions fixed.
Step-by-step
Match the opening phrase to its noun
Step 1Find where the phrase connects
The sentence starts with Having held, which tells us someone kept the test conditions fixed but leaves them unnamed. Where should we look for who did that? An opening describing phrase, called a modifier, describes the main noun right after its comma. That noun decides whether this sentence follows Standard English.
- Step 2
Name who kept the conditions fixed
Who held the channel’s size and the water’s speed constant? The first sentence says Fluid dynamicists Nia Patel and Tomas Ibarra tested the ridge patterns by exchanging panels, so the scientists running the test did that. We can predict a noun naming those people, not what they studied or measured.
- Step 3
Look past the scientists’ names
Does naming the scientists make Patel and Ibarra's measurements work? No, because its main noun is measurements; Patel and Ibarra's only tells us whose measurements they are. The version starting any observed differences in turbulence makes differences the main noun, while the panels' ridge patterns makes patterns the main noun. Measurements, differences, and patterns can’t hold the channel's dimensions and the water's average speed constant. Naming the scientists later in a comment doesn’t change which noun the opening phrase describes.
- Step 4
Put the scientists after the comma
The completion beginning Patel and Ibarra could attribute puts the scientists themselves right after the comma, so Having held describes them. Reading through the period also gives a complete sentence: the scientists could attribute the turbulence differences to the ridge patterns, not to changes in size or speed. Choice D.