\( \left.\begin{array}{l}\text { Which of the following is not allowed? } \\ \text { References to abstract classes. } \\ \text { Objects of abstract classes } \\ \text { Arrays of pointers to abstract classes. } \\ \text { Multiple pure virtual functions in a single } \\ \text { abstract class }\end{array}\right] \).

In the world of object-oriented programming, abstract classes are like blueprints that can’t stand on their own, which makes the idea of instantiating (or creating objects of) an abstract class a no-go. You can think of it like trying to build a real house from just the plans without actually constructing anything — it just doesn’t fly! However, don’t fret; you can certainly have arrays of pointers pointing to abstract classes! This allows you to manage collections of objects that share a common interface while still retaining their unique identities—kind of like having a mixed bag of fruit, where each piece has different flavors but belongs to the same grocery basket!