第35题: [单项选择]The babies would "smile and bubble" at the lights because ______. A. the lights were directly related to some basic "drives" B. the sight of the lights was interesting C. they need not turn back to watch the lights D. they succeeded in "switching on" the lights 参考答案:D 答案解析:[解析] 从文中最后一段的第二句“it was...skill”,可知此题答案为D。