if MACHO exist, the star will brighten (microlensing).
variable brightness or ml?
can identify difference - 1) ml equally affect all colors while the variable feature doesn't 2) frequency of ml is low - implying variable brightness feature occurs more often

1. The passage is primarily concerned with

A. outlining reasons why a particular theory is no longer credited by some astronomers the theory is argued by astronomers but isn't "no longer credited"
B. presenting data collected by a researcher in response to some astronomers' criticism of a particular line of reasoning
C. explaining why a researcher proposed a particular theory and illustrating how influential that theory has been it didn't explain why and didn't illustrate the importance neither. In order to comment on how influence it is, author will need to evaluate its application, but in this passage he/she didn't
D. showing how a researcher's theory has been used to settle a dispute between the researcher and some astronomers the theory is not used to settle a disputer - rather that theory is distributed, and then astronomers have some doubts which are clarified afterwards
E. describing a line of reasoning put forth by a researcher and addressing a contention concerning that line of reasoning correct answer, the passage begins with a reasoning, cite astronomer's doubt and then provide reason to address their concern


2. According to the passage, Paczynski's theory presumes that if MACHO's constituted the Milky Way's dark halo, occasionally a MACHO would

A. drift so as to lie in a direct line between two stars in the outer Milky Way "lie in direct line" is not mentioned
B. affect the light rays of a star in the Large Magellanic Cloud with the result that the star would seem for a time to brighten this coincides with "temporarily appear to brighten" and "cause the star's light rays to bend together..."
C. become obscured as a result of the microlensing of a star in the Large Magellanic Cloud "obscured" is the opposite description of what occurred in the passage
D. temporarily increase the apparent brightness of a star in the Large Magellanic Cloud by increasing the gravity of the star mix-up answer - the first half looks right while the 2nd is wrong, gravity change of the star is not mentioned
E. magnify each color in the spectrum of a star in the Large Magellanic Cloud by a different amount opposite to what the passage described - all colors are affects equally


3. It can be inferred from the passage that which of the following would constitute the strongest evidence of the microlensing of a star in the Large Magellanic Cloud?

A. The brightness of such a star is observed to vary at irregular intervals. "irregular intervals" is wrong - microlensing barely occurs for the 2nd time given "the chance that a second MACHO would pass in front of exactly the same star is minuscule"
B. The brightening of such a star is observed to be of shorter duration than the brightening of neighboring stars. the frequency comparison is not mentioned, all we know is the brightening is temporary
C. The red light of such a star is observed to be brighter than its yellow light and its blue light. all colors are affected equally, so this cannot be right
D. The red light, yellow light, and blue light of such a star are observed to be magnified temporarily by the same factor. correct answer
E. The red light of such a star is observed to have increased tenfold. mix-up answer, "tenfold" is mentioned" but the necessary condition for microlensing - which should be all colors being enhanced equally