Modern behaviorists generally believe that

A) all human and animal behavior can be described as simple responses to current, simple stimuli.
B) human thought is the only appropriate subject matter for psychologists to study.
C) behavior is a product of an individual's past history of stimuli and responses, as well as responses to current stimuli.
D) determinism is an obsolete concept.

Modern behaviorists believe that behavior is a product of an individual's past history of stimuli and responses, as well as responses to current stimuli, in other words, the environment interacts with an individual's genetic, physiological, and psychological components to determine behavior. This approach is known as the "contingency approach." Therefore, choice C is the best answer.

Option A is incorrect because behaviorism does not view behavior as a simple response to current, simple stimuli. Instead, it believes that behavior is shaped by complex interactions between an individual's history of stimuli and current stimuli.

Option B is incorrect because behaviorism is not limited to the study of human thought alone, but rather, it includes the study of how behavior is affected by environmental stimuli.

Option D is incorrect because determinism is still seen as a fundamental concept in behaviorism, which argues that all behavior is determined by the individual's experiences and the environment in which they live.