A diagnosis of mental retardation, now more commonly referred to as intellectual disability, typically means that a child:
A. Needs serious learning support in mental ability and behaviour.
This option correctly reflects the need for additional support in learning and adaptive behavior. The other options do not accurately represent the characteristics or implications of the diagnosis. For instance, individuals with intellectual disabilities can have varying levels of functional ability, and many can learn to read and write at a functional level. Additionally, having a mental age equal to chronological age would not align with the diagnosis, and many individuals with intellectual disabilities can and do function in society.