**Core Concept**
Recombinant human insulin is a form of insulin that is produced using genetic engineering techniques. This involves inserting the gene for human insulin into a microorganism, such as E. coli, which then expresses the protein. The resulting insulin is identical to the natural human insulin produced by the pancreas.

**Why the Correct Answer is Right**
The correct answer involves the production of recombinant human insulin through a process known as fermentation. In this process, the bacteria E. coli are genetically engineered to produce human insulin, which is then extracted and purified. This method allows for large-scale production of insulin with precise control over the product's characteristics. The use of recombinant DNA technology ensures that the resulting insulin is identical to the natural human insulin, with the same amino acid sequence and structure.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because recombinant human insulin is not made through the use of mammalian cells in culture. While mammalian cells can be used to produce insulin, the use of E. coli bacteria is a more common and cost-effective method.
**Option B:** This option is incorrect because recombinant human insulin is not made through the use of plant cells. While plant cells can be used to produce proteins, they are not typically used to produce insulin.
**Option C:** This option is incorrect because recombinant human insulin is not made through the use of animal tissues. While animal tissues can be used to produce insulin, the use of recombinant DNA technology allows for a more precise and controlled method of production.

**Clinical Pearl / High-Yield Fact**
Recombinant human insulin is used to treat diabetes mellitus, and is available in a variety of formulations, including short-acting, intermediate-acting, and long-acting insulins. It is essential to choose the correct type of insulin based on the individual patient's needs and circumstances.

**Correct Answer: C. E. coli**