Transcriptional repressor proteins (e.g., lac repressor), antisense RNA, and feedback inhibition are three different mechanisms that turn

Question:

Transcriptional repressor proteins (e.g., lac repressor), antisense RNA, and feedback inhibition are three different mechanisms that turn off the expression of genes and gene products. Which of these three mechanisms would be most effective in each of the following situations?
A. Shutting down the synthesis of a polypeptide
B. Shutting down the synthesis of mRNA
C. Shutting off the function of a protein
For your answers in parts A-C that have more than one mechanism, which mechanism would be the fastest or the most efficient?