Final answer:
The true statement about complex conversions between units is that they require using multiple conversion factors in a sequential manner to switch from one unit to another when no direct conversion is available.
Step-by-step explanation:
The correct answer to the question "Which of the following statements is true about complex conversions between units?" is (c) They require using multiple conversion factors in a sequential manner. Complex unit conversions often involve switching between units that have no direct conversion factor available.
Instead, you have to use one or more intermediate conversion factors that will allow you to cancel out the units you don’t want and end up with the unit you are looking to obtain.
For example, if you want to convert miles per hour to meters per second, you would need to use a conversion factor to convert miles to meters and another conversion factor to convert hours to seconds. A calculation like this clearly shows that such unit conversions are not always straightforward and cannot be performed directly without the use of conversion factors.
Therefore answer is (c) They require using multiple conversion factors in a sequential manner.