<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:The lac operon allows E. coli to effectively utilize lactose when it is available, and not to produce unnecessary proteins. Which of the following genes is constitutively expressed and results in the repression of the lac operon?? A: LacI, B: LacZ, C: LacY, D: LacA, E: CAP,  <response>: This is a question about the lac operon in E. coli. The lac operon allows E. coli to produce proteins to metabolize lactose when lactose is available, but repress production of those proteins when lactose is absent to avoid wasting resources. The question asks which gene is constitutively expressed and represses the lac operon when lactose is absent. LacZ encodes beta-galactosidase which metabolizes lactose. LacY encodes a lactose permease. These are induced as part of the lac operon when lactose is present. LacA is not a gene involved in the lac operon. CAP is involved in activation of the lac operon when glucose levels are low.LacI encodes the lac repressor which binds to the operator region of the lac operon to prevent transcription when lactose is absent. LacI is expressed constitutively at a low level. Therefore, LacI is the gene that is constitutively expressed and represses the lac operon in the absence of lactose.A: LacI 