This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
[{'content': 'Which form of alginic acid, which is present in alginate, provides strength to the impression material? \nSelect and explain. \nA. Alpha-d-mannuronic acid, B. Alpha-d-guluronic\xa0acid, C. Both of the above, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Alpha-d-mannuronic acid provides flexibility, which is extracted from certain brown seaweed, is a linear copolymer of β-D-mannuronic acid and α-L-guluronic acid. Mannuronic and guluronic acids are epimers. It is known that the block structure within the alginic acid can vary significantly. Alginates with higher guluronic acid levels normally show a stronger interaction with calcium, and hence, yield greater gel strength. For impression-making purposes, the alginate is richer in mannuronic acid.\nRef: Phillips 12 ed page no 171', 'role': 'assistant'}]