20. The information for this LSAT main point question may be found by reading lines 5 to 7. (C) paraphrases this information and is correct.
(A) is wrong because of the word "overall", which would need to be "later", and "makeup" which would need to be something such as "structural development".
(B) seems OK until the comma, but polarity for is not dependent on the simplicity or complexity of an organism.
(D) states "embryos" which means all embryos, but the rest of (D) provides information about how the fruit fly and nematode achieve early polarity, but lines 38 to 40 state that more complex organisms achieve polarity differently.
(E) contradicts the passage which states that polarity is established in different ways, not "essentially the same".
21. The information for this LSAT support inference question appears in lines 42 to 44. Choice (C) is the correct choice. Notice that the choice is supported, but cannot be definitively proven true by the passage. Learning to distinguish support questions from must be true questions is an essential skill to doing well on the LSAT.
(A) refers to speed, but no information exists in the passage about this other than the making of a fruit fly egg (lines 19 to 20) and for transformation of a fruit fly egg to larva (lines 21 to 22), but no information exists for more complex organisms regarding speed and so a comparison may not be supported.
(B) refers to "most" (more than half), but the passage only tells us about "some" (frogs). Also ,the passage states "thought to" (line 36), which is different from "have determined".
(D) refers to the number of observations that may be generalized but the passage does not provide support for a number. If anything, (D) apparently goes against the passage -- see lines 55 to 57.
(E) is similar to (A) by referring to a connection between an organism's simplicity and the speed at which it develops, but no information connects these, nor does the passage provide information to support a comparison.
22. This LSAT "suggest" inference question requires that you read each choice to determine which has support.
(A) refers to behavior, which is never mentioned in the passage.
(B) goes against the passage -- see lines 45 to 47.
For (C), the passage states that polarity apparently does not occur in the egg before fertilization. See lines 39 to 41.
For (D), see lines 39 to 41 (polarity different), and lines 49 to 51 (visual system similar).
(E) seems to make sense, but do not bring in any outside information -- only rely upon the information in the passage. (E) refers to how long a human embryo develops but the passage makes no mention of this, and a comparison may not be made.
23. The answer to this LSAT explicit information question appears in lines 37 to 42, and (A) is the correct choice.
(B) refers to fruit flies -- see lines 16 to 17.
(C) refers to the nematodes -- see lines 26 to 30.
(D) refers to frogs -- see lines 35 to 37.
(E) contradicts the passage information -- see lines 38 to 39.