ElementSPCASTHTCOCCiron20%28%90%98%potassium44%74%97%100%sodium45%75%99%100%Earth's atmosphere is bombarded by cosmic dust originating from several so...
GMAT Information and Ideas : (Ideas) Questions
| Element | SPC | AST | HTC | OCC |
|---|---|---|---|---|
| iron | 20% | 28% | 90% | 98% |
| potassium | 44% | 74% | 97% | 100% |
| sodium | 45% | 75% | 99% | 100% |
Earth's atmosphere is bombarded by cosmic dust originating from several sources: short-period comets (SPCs), particles from the asteroid belt (ASTs), Halley-type comets (HTCs), and Oort cloud comets (OCCs). Some of the dust's material vaporizes in the atmosphere in a process called ablation, and the faster the particles move, the higher the rate of ablation. Astrophysicist Juan Diego Carrillo-Sánchez led a team that calculated average ablation rates for elements in the dust (such as iron and potassium) and showed that material in slower-moving SPC or AST dust has a lower rate than the same material in faster-moving HTC or OCC dust. For example, whereas the average ablation rate for iron from AST dust is 28%, the average rate for ______
Which choice most effectively uses data from the table to complete the example?
iron from SPC dust is \(20\%\).
sodium from OCC dust is \(100\%\).
iron from HTC dust is \(90\%\).
sodium from AST dust is \(75\%\).
Step 1: Decode and Map the Passage
Part A: Create Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| "Earth's atmosphere is bombarded by cosmic dust originating from several sources: shortperiod comets (SPCs), particles from the asteroid belt (ASTs), Halley-type comets (HTCs), and Oort cloud comets (OCCs)." |
|
| "Some of the dust's material vaporizes in the atmosphere in a process called ablation, and the faster the particles move, the higher the rate of ablation." |
|
| "Astrophysicist Juan Diego Carrillo-Sánchez led a team that calculated average ablation rates for elements in the dust (such as iron and potassium) and showed that material in slower-moving SPC or AST dust has a lower rate than the same material in faster-moving HTC or OCC dust." |
|
Part B: Main Point
Main Point: Research shows that cosmic dust from faster-moving sources has higher ablation rates than dust from slower-moving sources.
Step 2: Interpret the Question Precisely
What's being asked? Which choice most effectively uses data from the table to complete the example about iron ablation rates.
What type of answer do we need? A data point from the table that logically completes the comparison.
Step 3: Prethink the Answer
The example starts by mentioning iron from AST dust at 28%. Since the passage argues that faster-moving dust (HTC/OCC) has higher rates than slower-moving dust (SPC/AST), the completion should show a higher rate from faster-moving sources using iron to maintain comparison coherence.
iron from SPC dust is \(20\%\).
✗ Incorrect
Shows iron from SPC dust at 20% - This is backwards since SPC (20%) is lower than AST (28%), not illustrating the speed-ablation relationship.
sodium from OCC dust is \(100\%\).
✗ Incorrect
Shows sodium from OCC dust at 100% - Switches from iron to sodium, breaking comparison coherence despite showing higher rate.
iron from HTC dust is \(90\%\).
✓ Correct
Shows iron from HTC dust at 90% - Maintains iron comparison while showing dramatic difference between slower AST (28%) and faster HTC (90%). Perfectly illustrates the passage's point.
sodium from AST dust is \(75\%\).
✗ Incorrect
Shows sodium from AST dust at 75% - Switches elements and uses same slower-moving source type, not effectively showing speed contrast.