The correct answers are A and D.
In order to write a good summary, it is important to make it objective. By adding the phrase "it is petrifying" the writter is adding his personal feelings towards the subject. Therefore, that part should be deleted.
Also, to make the summary clearer and more complete, the phrase "and spread throughout the human species" should be added at the end of the sentence. This would help create a better understanding of the topic at hand.