Escherichia coli is used extensively in biological research as it is

Explanation

Let's explain each option individually: a) Easily cultured: This option is correct. Escherichia coli (E. coli) is easily cultured in the laboratory, making it a popular choice for biological research. It is a fast-growing bacterium that can be easily cultivated on various culture media, such as agar plates or in liquid media. Its rapid growth and simple nutrient requirements make it convenient for researchers to study and manipulate in the laboratory. b) Easily available: While E. coli is a commonly found bacterium in the environment, this option is not the primary reason it is extensively used in biological research. Its widespread presence in nature does contribute to its accessibility for researchers, but the main reason for its widespread use is its ease of culture and manipulation in the laboratory. c) Easy to handle: This option is related to the ease of culturing and manipulating E. coli in the laboratory. E. coli is indeed easy to handle due to its simple growth requirements, well-established protocols for transformation and manipulation of its genetic material, and well-characterized molecular biology tools available for studying this bacterium. d) Easily multiplied in the host: This option is not entirely accurate in the context of biological research. While E. coli is capable of multiplying rapidly in its natural host, the human intestine, the primary reason for its use in biological research is its ability to multiply rapidly and be easily cultured in the laboratory setting. The focus is on its laboratory applications, rather than its natural multiplication in the host. In summary, the correct answer is a) Easily cultured. Escherichia coli (E. coli) is extensively used in biological research because it is easily cultured in the laboratory due to its fast growth, simple nutrient requirements, and well-established protocols for manipulation and genetic engineering. Its ease of culture makes it a valuable model organism for studying various biological processes and conducting experiments in the field of molecular biology, genetics, and microbiology.