Which of the Following Has Not Been Shown to Be

Which of the following has not been shown to be true of children with math disabilities?

A) They tend to use less-sophisticated arithmetic strategies than typically developing children.
B) They tend to use fact retrieval less often when solving simple arithmetic problems than typically developing children do.
C) Their practice at fact retrieval appreciably improves their performance.
D) They have difficulty keeping number names in their working memories.