Siegler and Colleagues Studied Children's Use of Strategies on Arithmetic

Siegler and colleagues studied children's use of strategies on arithmetic problems and found that

A) children of a given age do not vary much in the strategies they prefer and the skill with which they execute those strategies.
B) children at any point in development may employ a number of different strategies, sometimes using one approach and at other times using another.
C) with development, there is a progression from less efficient to more efficient strategies, but this is the exception rather than the rule.
D) All of the alternatives are correct.