Mastering C++: A Comprehensive Quiz Based on 'Thinking in C++

Upcasting is the process of converting a variable of a derived class into a variable of its base class. This allows the derived class object to be used in place of the base class object, which can be quite useful in object-oriented programming. Option A, which is stating that upcasting simplifies exception handling, is incorrect because upcasting itself does not handle exceptions and does not have any connection to exception handling. Option B, which states that upcasting allows creating new base classes, is incorrect because new base classes can be created without upcasting. Option D, which states that upcasting optimizes storage allocation, is incorrect because upcasting itself does't have any effect on storage allocation. In summary, option C is the correct answer because through upcasting, derived objects can be treated as their base class, which provides more flexibility and ease in manipulating objects in different classes.