A dog trainer gives a dog a treat every third time the dog sits after the trainer says "sit." What BEST describes the schedule of reinforcement under which the trainer is controlling the dog's behavior? a. Fixed ratio b. Variable interval c. Variable ratio d. Fixed interval

The diagram below shows the layers of a rock having a trilobite: a rock column labeled rock is shown. the column has three layers. the bottommost layer of the rock has one shaded rhomboid shape, the middle layer has a rhombus with a diagonal along with two identical organisms marked as, trilobite, in the key, the top layer has two semicircles. a key is shown on the right side of the diagram. the shaded rhombus is marked as a, the rhombus with the diagonal is marked as b, the semicircle is marked as c which statement about the rock fossils is true?