Answer:
"An amplified unknown hot agent; high-hazard work".
Step-by-step explanation:
The central idea or theme of the passage in the question is the dangerous situation of any work done in a containment zone. Containment zones are those sites or areas that are 'contained' or rather isolated or restricted for common entrance and view. So, when the speaker talks of the work that had to be done in the containment zone, she stressed on the severity of the situation. The animal to be tested "had died of an amplified unknown hot agent" which renders the work "high-hazard".
Thus, these two phrases support the central theme of the dangerous condition of the work to be done.