what does it mean when a good shifts to the left on a demand curve

Don't use chat gpt otherwise I downvote the answer    The graph below depicts the market for tea. Suppose the price of coffee increases (the two goods are substitutes in consumption). Which of the following statements shows the change in the market for tea? a) The demand curve will shift from D₁ to D₂. b) The demand curve will shift from D₁ to D3. c)There will be a change in the quantity demanded from Point a to Point b. d) There will be a change in the demand from point b to point a

What does the demand curve shows the relationship between?

Two students, Nick and Sofia, are discussing normal and inferior goods. Nick says that if Frodo buys more beer when the price of beer goes up, then beer must be an inferior good for Frodo. If, on the other hand, he buys less beer when the price of beer goes up, then beer must be a normal good for Frodo. Sofia disagrees: "Normal and inferior goods are about income changes, not price changes. Therefore, we do not have enough information: beer could be an inferior or normal good in either of these cases." Do you agree or disagree? Carefully explain your point of view. Support your argument with graphs of income, substitution and total effects (please put beer on the horizontal axis and the other goods on the vertical axis). Please assume that Frodo's preferences over beer and other goods are strictly convex and satisfy "more is better" assumption.