Final answer:
The correct prepositions for the sentences are 'by' and 'of'. 'By' is used to indicate the author of a book and 'of' to denote what is in a picture.
Step-by-step explanation:
In English, we often use specific prepositions in set phrases or 'collocations'. For your examples, the correct prepositions would be 'by' and 'of'. Thus:
- The book was written by Mark Twain.
- I'll show you the picture of the palace.
'By' is used to indicate the author of a book and 'of' is used to indicate who or what is in a picture. This is an integral part of mastering English grammar.
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