The right answer is ''there are''
I got the answer from here
It is simply that we determine the verb according to the subject and the trick here is that ''there'' is not the actual subject where as ''a book, two pens and four pencils'' is the compound subject and as you can see it is plural. You can read it as ''A book, two pens and four pencils are there on the table'' it makes it easier to read that way because you could easily find the real subject for your verb. And to can it even clearer it gave you and example, try replacing the word there (which we just proved not to be the actual subject) with the word ''Bob'' ... Bob is a book, two pens and four pencils.. here I am making a statement that Bob is actually a book and .... no matter what the subject is Bob that is a singular subject so it will always get ''is''
Hope this makes sense and answers your question ^-^