This says nothing about humans being regarded as natural objects, so it can’t be right. The conclusion is about humans being regarded only as natural objects, yet the premises say nothing about this. The correct answer must discuss how humans being regarded only as natural objects will lead to a moral decline, but (A) doesn’t do that.

We know from the argument’s premises that when humans lose their sense of responsibility for their actions, it leads to a general moral decline. (B) adds that humans who regard themselves only as natural objects will lose their sense of responsibility for their actions, so humans regarding themselves only as natural objects will lead to a general moral decline.

The argument doesn’t address people who have a sense of shame for their moral transgressions. The argument only discusses people who feel unashamed when they act immorally.

The argument already says that some scientific theories hold that human beings aren’t responsible for their actions. The correct answer choice must explain how acceptance of these sorts of theories, where humans are just beings that are subjected to forces outside of their control, leads to a general moral decline.

The argument doesn’t discuss scientific explanations that regard human beings as in some respects independent of the laws of nature. The correct answer must discuss how humans being regarded only as natural objects will lead to a moral decline, but (E) doesn’t do that.