Correct Answer: Granny said to Nina that she didn't know why she thought it was so wonderful.

Solution : The correct choice is the second option .

Narration Conversion:

• Said is changed to told in the reported speech.
• That is added to link the main clause to the reported clause.
• The first person pronoun I is changed to the third person pronoun she .
• Don't know is changed to did not know , as the simple present tense is changed to the simple past tense in the reported speech.
• Think is changed to thought .

Therefore, the correct sentence is: Granny told Nina that she didn't know why she thought it was so wonderful .