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Table 10 Excerpt 4: A segment of discourse from group E’s discussion (lines 21 to 32)

From: Promoting productive argumentation through students' questions

Turn of talk Student Discourse
21 E: What do you think was the cause of death?
22 S: I believe its drowning.
23 E: I thought so too. Okay, that’s our claim. Let’s find all the evidence we can to support this.
24 A: To be drowned, water must enter her lungs. How did the water enter her lungs?
25 S: The killer pushed her head down into the river water, so as she grasped for air, she inhaled the water into her lungs.
26 A: Then, beside river water, the content in the lungs was red? What could that red thingy be? Also, what are potassium ions? How come they are found so high in the blood plasma?
27 S: The red thingy is haemoglobin.
28 A: But haemoglobin is found inside the RBC.
29 S: Yes, but RBC has lysed because they gained water by osmosis so haemoglobin released.
30 E: RBC also contains potassium ions. So when RBC burst, these ions were released and remember Mrs. Liow mentioned when the ions are out-of-balance in our plasma, can lead to cardiac arrest. So it must be this that explains for the high potassium ions.
31 A: Then what about the intravenous injection? Hormones … what was that for?
32 E: The content of the injection is hormones. Hormones are not lethal and not strong enough to cause cardiac arrest.