This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
All of the following interaction occurs between antigen and antibody Except 
Select and explain. 
A. Ionic bond, B. Covalent bond, C. Hydrogen bond, D. Vanderwalls forces
B: Covalent bond
Answer: B: Covalent bond 
Explanation: The primary stage reaction of antigen and antibody is reversible ,this combination being affected by weaker molecular forces like vanderwaal's forces,ionic bonds,and hydrogen bonding, rather than by the firmer covalent bonding. Ref: anantnarayan and panikers 10th edition