Answer:
B. The ice cream flavor board should be constantly updated.
Explanation:
The main idea of the passage is described in the first line of this paragraph i.e. <em>"The trouble is, of course, that they put up that sign..."</em>. This problem/idea is discussed in next few lines. In the last part of this passage, the writer tells the readers about children's special abilities to identify the flavors just by names, without the signs.
Option A is not correct firstly because the writer has clearly stated the main idea by calling it <em>"the trouble" </em>and secondly the passage is about ice-cream and not about children's abilities.
Option C is incorrect because the passage says nothing deciding on flavor of ice creams.
Option D is incorrect because it is contrary to what is described in the passage. Passage says they don't update signs. Moreover adding new flavors is not result of running out of flavor.
