Parts of the following sentence have been highlighted and given as options. Select the option that contains an error.
When I bought the book, I thought it will be interesting.

Correct option is C

The error in the sentence is the use of "will" in the phrase "I thought it will be interesting." Since the main verb "thought" is in the past tense, the subordinate clause should also reflect a past perspective. The correct phrase is "I thought it would be interesting," using "would" to indicate the future from the past perspective.