Although there is disagreement over the role of population growth,which statement on the optimum population size for the world do a number of experts agree on? 

A)  Between 20 and 40 billion is the optimum population size. 
B)  Optimum population size is a meaningless concept. 
C)  There is no limit to how many people the planet can support. 
D)  There is an upper limit of about 100 billion.

A number of experts believe that the concept of an optimum population size is meaningless, as it is dependent on various complex factors such as resource availability, distribution, and technology. Additionally, there is no consensus on the upper limit of how many people the planet can support, as different studies and models suggest vastly different numbers. Therefore, choice B is the most accurate statement.