Final answer:
The correct reply from Sam to Mr. Bixby when asked about the purpose of knowing the names of the points on the river is "To help me learn the river, sir."
Step-by-step explanation:
The correct reply from Sam to Mr. Bixby when asked the purpose of knowing the names of the points on the river is "To help me learn the river, sir." This response indicates that Sam wants to gain knowledge about the river and familiarize himself with its different points. Sam's intention is to use this knowledge for understanding the river better. This answer shows Sam's willingness to learn and improve his understanding of the subject matter.
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