The word that best replaces curious in the sentence is ;
Interested
The word curious refers to the act of being eager to find out the details about something. It is synonymous with the word interested which also connotes the eagerness to learn about something.
Andy's curiosity refers to his interest in trying to see how bread was made. Thus the statement can be rewritten this way;
Andy was<u> </u><u>interested </u>to see how bread is made.
This replacement leaves the sentence with the same meaning. Therefore, the word that serves as the best replacement is interested.
