Instructions: This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
Input: Often 'b' & 'p' are interchangeable, for example 'baggage' becomes 'pagas', 'lob' (to throw) becomes 'loopima'. The initial letter 's' is often dropped, for example 'skool' becomes 'kool', 'stool' becomes 'tool'.
Output:
What two letters can be replaced with each other a lot of the time in Estonian?