LSAT 117 | Section 3 | Logical Reasoning: Q24

LR Question 24 Explanation

QUESTION TEXT: Science journalist: Brown dwarfs are celestial objects…

QUESTION TYPE: Most Strongly Supported

FACTS:

1. Brown dwarfs are celestial objects.
2. They have more mass than planets but less than stars.
3. Brown dwarfs are identified by their mass and whether they have lithium.
4. Stars at least as massive as the sun have lithium.
5. This is because their internal furnaces can’t mix it all.
6. Stars with less mass than the sun have no lithium. Their internal furnaces mix it all.
7. A brown dwarf has no nuclear furnace (and therefore has lithium)

ANALYSIS: Many people find this question difficult. When the LSAC writes a long, dense science question they often compensate by making the answer choices easy to eliminate if you understood what you read. Read questions twice if you don’t understand them. It will speed you up and prevent you wasting time with wrong answers.

All four wrong answer choices talk about “any celestial object.” We don’t know anything about all celestial objects. We only know about stars and brown dwarfs.

For example, Earth is smaller than the sun and brown dwarfs. But we do have lithium. The rules don’t apply to things that aren’t stars or brown dwarfs.

___________

1. The problem is that this talks about any celestial object. We only know about stars and brown dwarfs. 
2. Same as A. We only know about two of the many types of celestial objects.
3. CORRECT. This is a backwards way of saying: brown dwarfs have lithium. That has to be true because they have no nuclear furnace and can’t mix their lithium. 
4. This is only true of stars. It might not be true for all celestial objects.
5. Again, the problem is the term “celestial object.” Lots of planets such as Earth have lithium despite being smaller than a brown dwarf.