15. The bacterial growth in liquid culture media can be observed as the increase in the __ a.Colony number b. Turbidity C.Color d. Temperature 16. Which one of the followings is not a correct definition? a.Naked viruses are more resistant to environmental conditions b. Thermophilic bacteria live best in the human body C. Viruses can be observed under the light microscope d.Parasites are eukaryotic 17. In a bacterial growth chart, what is the name of the stage that 'reproduction rate=death rate' a.Lag phase b. Log phase C. Death phase d.Stationary phase 18. If an organism has complex nutritional requirements needs __ to be added to the culture media. a. Nitrogen sources b. Magnesium C. Growth factors d. Carbon sources 19. If a bacteria can divide in every 30 minutes, how many bacteria will the colony include within 12 hours? a. 1times 2^10 b 1.6times 1^10 C. 1times 2^24 d 30times 2^10 20. __ bacteria are the bacteria group which can not grow on a specific culture media easily and nee extra supplements to be added to the culture medi. a. Microaerophilic b. Aerotoleran C. Fastidious d. Heterotrophs

15. The correct answer is b. Turbidity. Bacterial growth in liquid culture media can be observed as an increase in turbidity, which indicates the presence of bacteria in the medium.<br /><br />16. The correct answer is b. Thermophilic bacteria live best in the human body. Thermophilic bacteria prefer high temperatures and are not typically found in the human body. The other options are correct: naked viruses are more resistant to environmental conditions, viruses can be observed under a light microscope, and parasites are eukaryotic.<br /><br />17. The correct answer is d. Stationary phase. In a bacterial growth chart, the stationary phase is the stage where the reproduction rate equals the death rate, resulting in a stable population size.<br /><br />18. The correct answer is c. Growth factors. If an organism has complex nutritional requirements, growth factors need to be added to the culture media to support its growth.<br /><br />19. The correct answer is c. $1\times 2^{24}$. If a bacterium can divide every 30 minutes, then within 12 hours (which is 24 half-hour intervals), the colony will include $1\times 2^{24}$ bacteria.<br /><br />20. The correct answer is c. Fastidious. Fastidious bacteria are those that cannot grow easily on a specific culture media and require extra supplements to be added to the culture media for their growth.