<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A biology graduate student is performing an experiment in the immunology laboratory. He is researching the recombination activation genes RAG1 and RAG2 in order to verify the function of these genes. He then decides to carry out the experiment on knock-out mice so that these genes will be turned off. Which of the following changes should he be expecting to see?? A: Defect of NADPH oxidase in phagocyte, B: Total lack of B and T cells, C: Deficiency in CD40L on activated T cells, D: Absence of CD18 in leukocytes, E: The mice should be asymptomatic,  <response>: This is a question about the expected results of knocking out the RAG1 and RAG2 genes in mice. RAG1 and RAG2 are involved in VDJ recombination, which is necessary for the production of functional B and T cell receptors. Knocking out these genes should prevent VDJ recombination and maturation of B and T cells.Choice A about NADPH oxidase is unrelated to RAG12 and BT cell development. Choice C about CD40L and Choice D about CD18 are also unrelated. Choice E is incorrect because knocking out RAG12 should cause an immunodeficiency phenotype.Therefore, the expected result is choice B - a total lack of B and T cells due to inability to produce functional antigen receptors.B: Total lack of B and T cells 