Question

Make the following sentence more active : five books is the series have been writing by the author

Answer 1

Let us assume that you meant to write:
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"Five books in the series have been written by the author."
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In that case, let us make the sentence more "active" (as opposed to the "passive" form in which it is written) by re-writing the sentence as:
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"The author has written five books in the series."
→ This is our answer.

Answer 2

The author has written five books in the series.

Step-by-step explanation:

Assuming the original sentence reads as:

"Five books in the series have been written by the author".

In order to turn the sentence from its passive form to its active form, it is necessary to identify the object that performs the action and the one that receives it, and then proceed to switch their order.

Object that performs the action: The author.

Object that receives the action: Five books in the series.

Now switching the order:

The author has written five books in the series.