Rocket engines are most effective

Answer choices

1. A

   Irrelevant Comparison: more difficult2% picked this

   Equipping a rocket's engines with both short and long nozzles is not significantly more difficult than equipping them

   The author's argument has nothing to do with which nozzle setup would be easier or harder to install. It is purely about which nozzle setup would be required if your goal were "working most effectively throughout the ascent". If we negated this answer and said, "Hey author, it is significantly more difficult to equip a rocket with both short and long", that doesn't weaken the conclusion at all. He isn't saying short + long is feasible, affordable, easy, etc. He's only saying it's required if you wanted a rocket to work most effectively throughout the ascent.

   2%
2. B

   Correct64% picked this

   At some point during their ascents, all rockets will pass through the

   Why this is right

   This has the new language from the conclusion (during their ascent, all rockets). Since the author thinks that all rockets need a long nozzle (which is only needed for working most effectively in the upper atmosphere), that must mean that the author is assuming that all rockets go through the thin upper atmosphere during their ascent. If we negated this answer, it would turn into an objection: Hey, author, not all rockets pass through the upper atmosphere during their ascent. Some of them stay at low altitudes, so they only need a short nozzle to work most effectively.

   Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.

   64%
3. C

   Too Strong: cannot reach3% picked this

   A rocket with only short nozzles on its engines cannot reach

   The author was never saying that you need a long nozzle to reach the upper atmosphere, only that you would need it for your rocket to work most effectively in the upper atmosphere.

   3%
4. D

   Too Strong: to work effectively15% picked this

   For a rocket to work effectively, its engines' exhaust gases must leave the nozzles at the same pressure as the surrounding

   The argument established that for a rocket to work most effectively, the exhaust gases should match the pressure of the surrounding atmosphere. This answer is going way farther than that, saying that for a rocket to work effectively at all, they exhaust gas must match the pressure of the surrounding atmosphere. When we say stuff like, "for this zinc lozenge to work most effectively, you shouldn't eat any citrus foods within 30 minutes of taking it", we're not saying, "If you do eat citrus foods within 30 minutes, it isn't effective at all." We're just saying, "it's less effective".

   15%
5. E

   Too Specific: one engine has both16% picked this

   For a rocket to work most effectively at both low and high atmospheric pressures, it must have at least one engine that has both

   Although this sounds like a tempting inference we could draw from the paragraph, it gets too specific. If a rocket had four engines, two of them with short nozzles and two of them with long nozzles, then it could use the short nozzle engines at low altitudes and the long nozzle engines at high altitudes. Why does it need to have at least one engine that has both nozzles? (Is it even possible for a single engine to have more than one nozzle on it?) The specificity of this answer is what we want to chase us away. The conclusion is just saying, "all rockets need both short and long nozzles on their engines", but it never specifies that they need a short and long on the same engine.

   16%