单选题 The passage suggests that the principal effect of the state action limitation was to ______.

A、 allow some discriminatory practices to continue unimpeded by the Fourteenth Amendment
B、 influence the Supreme Court's ruling in Brown v. Board of Education
C、 provide expanded guidelines describing prohibited actions
D、 prohibit states from enacting laws that violated the intent of the Civil Rights Act of 1866

【正确答案】 A

【答案解析】见文中第二段which asserts that“private”decisions．．．arc insulated from the reach of the Fourteenth Amendment．．．，insulated from使隔离，不受影响，选项A中unimpeded不受阻止的，与之意思对应。