A researcher tries to make sure that subjects in the experimental and control groups are very similar to each other in order to reduce the effects of

Families with stepchildren, foster children, or adoptive children experience greater challenges in developing secure attachments, because

the children frequently run away from such arrangements. some children remain strongly attached to their birth parents. the parents tend not to fully accept the children into their families. the parents' biological children in the family are threatened by "outsiders."

Retroactive interference of long-term memory means ______

a. new material interferes with remembering old material b. new material represses short-term memories c. old material interferes with remembering new material d. old material has eliminated memories of new material