Final answer:
The two negative aspects of indirect count are the need for skilled personnel and specialized equipment, and its susceptibility to biases and errors, which can affect the accuracy of cell density estimates.
Step-by-step explanation:
The two negative things about indirect count are B) Requires skilled personnel and specialized equipment, and C) Subject to bias and errors. Indirect methods, such as using a spectrophotometer to measure turbidity, can be efficient but also have drawbacks. These methods often require skilled personnel to perform the measurement and interpret results, as well as the use of specialized equipment that may not be available in all settings. Additionally, indirect counts can be subject to various biases and errors. Factors like the presence of non-living particles can affect turbidity readings, leading to inaccurate estimates of cell density.