Answer:
obsessive ideas
Step-by-step explanation:
Obsessive ideas are characterized by uncontrolled thoughts of distressing thoughts and images which are usually accompanied by uneasy feeling and behavioral routines that seem reoccurring. The professor might start getting scared of falling ill or worry over little things such as papers that may contain germs. He may also indulge in compulsive behaviors that are obsessive, such as frequent washing of the hands.