Think of this test as a hormone response check rather than a memorised list. First the cow must be bred, so insemination (A) always comes first. About three weeks later, the milk cistern is drained through a cannula so that no old milk is left to confuse the result, so (D) comes next. Only after the cistern is empty does it make sense to inject the Dinoprost dose (B), because the test measures whether this injection triggers a fresh oxytocin driven milk let down. The final step is watching the teat for that let down within about a minute (C), which tells whether the corpus luteum, and so the pregnancy, is still active. $\boxed{(A), (D), (B), (C)}$