A involves random assignment of participants and manipulation of the causal variable, while a may have manipulation of the causal variable, but never involves random assignment of participants

true experiment, non-experiment

Explanation: A true experiment is the type of experiment carried out in which a conscious effort is made to control all the other variables in the experiment except the one variable under study/observation. This is often referred to as the most accurate form of research as it can be used to prove or disprove a hypothesis, given that all other variables are constant but one.

A non experiment on the other hand is a type of experiment where there's no room for control over or manipulation of the predictor variable, which means the researcher has to make inferences and conclusions from observations and interpretations. Such experiments are never conclusive enough to prove or disprove hypotheses.

the answer to this question is d

because he is that the right