单选题
The children who were selected for the experiment gained more IQ points than the others because they were ______.
【正确答案】
D
【答案解析】推理题。根据文中“Teachers…had given them more positive reinforcement．”(教师给了他们更多的正面帮助。) positive reinforcement中包含了很多正面因素如表扬、褒奖、鼓励等。所以根据文义，选[D]正确。