Which of the following is false with regard to prevalence ?: (A) It is a product of incidence and duration., (B) It can be determined by a cross-sectional studies., (C) It is a rate., (D) Prevalence is point prevalence unless otherwise specified.
Answer is C. Prevalence:

Prevalence is defined as  "the total number of all individuals  who  have an attribute or disease at a  particular time  (or  during  a particular  period)  divided  by  the population at risk  of having the attribute or disease at this point in time or midway through the  period. 
Although referred to as a rate, prevalence rate is really a ratio. 
Prevalence is of two types : 

        (a) Point prevalence 
        (b) Period prevalence 

When  the  term  "prevalence  rate"  is  used,  without any  further  qualification,  it  is  taken  to  mean  "point prevalence".