Hidden Not Overridden

None of the declarations in Lru uses the override keyword. Calls go through a Base*.

struct Key;

struct Base {
    virtual std::size_t size() const;
    virtual void        evict(const Key& k);
    virtual Base*       clone() const;
    virtual void        flush(int level = 0);
    virtual ~Base();
};

struct Lru : Base {
    std::size_t size();              // A
    void        evict(Key& k);       // B
    Lru*        clone() const;       // C
    void        flush(int level = 3);// D
};

More than one of these fails to override the base version. Which ones?