Question

read the passage. there are several questions about this passage.
linus pauling (1901-1994) was an american scientist. he studied dna, the material that carries a living organism’s genetic information.
from the shape of dna
1
like most other scientists, pauling was not interested in dna until 1952, even though swiss biologist friedrich miescher had discovered dna in 1869. but what was dna? scientists knew only a little. it came in long strands, and each strand had a phosphorus - sugar backbone. there were also nucleic bases, which stuck out from the backbone like knobs on a spine. but the shape of the strands and how they linked up were mysteries—important mysteries. as pauling showed with hemoglobin, shape can affect how molecules work. soon the shape of dna became the most important question in biology.
2
and pauling, like many others, assumed he was the only one smart enough to answer this question. this wasn’t, or at least wasn’t only, arrogance: pauling had simply never been beaten before. so in 1952, pauling sat down at his desk in california to crack dna. he decided, incorrectly, that the bulky nucleic bases sat on the outside of each strand with the phosphorus - sugar backbone toward the molecule’s core. pauling also reasoned that dna was a triple helix, with three ribbons of the phosphorus - sugar backbones forming a spiral.
unfortunately for pauling, his data came from a dried - out dna sample, which made the molecule seem more complicated. but on paper, all this seemed possible.
3
everything was humming along nicely until pauling asked a graduate student to check his calculations. the student did and was soon tying himself in knots trying to see where he was wrong and where pauling was right. eventually, the student pointed out to pauling that something about his theory didn’t seem quite right.
4
the graduate student explained his thinking, and pauling, being pauling, politely ignored him. it’s not clear why pauling bothered to have someone check his work if he wasn’t going to listen, but pauling’s reason for ignoring the student is clear. he wanted scientific...
choose two ways the illustration after paragraph 9 best clarifies information for the reader.

1. the illustration explains how important the phosphorus - sugar backbone is in dna.
2. the illustration reveals the actual names of the four bases discussed in the passage.
3. the illustration supports the idea of why dna is sometimes referred to as a kind of blueprint.
4. the illustration provides a concrete example of what the widely accepted dna model looks like.
5. the illustration details the importance of the four bases and why they fit snugly with the backbone.

Explanation:

To solve this, we analyze each option:

1. The passage doesn’t emphasize the “importance” of the phosphorus - sugar backbone; it just describes its existence. So this is incorrect.
2. If the passage discusses four bases, an illustration revealing their actual names would clarify that information for readers. This is a valid way the illustration can help.
3. The passage doesn’t connect DNA being a “blueprint” to the illustration’s role. So this is incorrect.
4. The passage talks about models of DNA (like Pauling’s triple helix). An illustration showing the widely accepted DNA model would provide a concrete example, clarifying the concept. This is valid.
5. The passage doesn’t focus on the “importance” of the four bases or why they fit with the backbone. So this is incorrect.

Answer:

1. The illustration reveals the actual names of the four bases discussed in the passage.
2. The illustration provides a concrete example of what the widely accepted DNA model looks like.