Final answer:
The correct understanding is that the progression from HIV to AIDS varies between individuals and can span many years, especially with the use of proper medication.
Step-by-step explanation:
The client's statement that indicates a correct understanding of the timing of progression of HIV to acquired immunodeficiency syndrome (AIDS) is option C) 'There's no specific time; it varies for different individuals.'
HIV infection can progress to AIDS at different times for different individuals. The development of AIDS from HIV is a complex process that typically takes years. With the advent of antiretroviral therapy, this progression can be significantly delayed, to the point that people with HIV can live long and healthy lives if the virus is managed correctly. AIDS is diagnosed when the CD4 T-cell count falls below a certain threshold or when opportunistic infections occur due to the weakened immune system.