2级

单选题Evidence came up which specific speech sounds are recognized by babies as young as 6 months old.

参考答案:C进入在线模考
本句意为:六个月大的幼儿能够识别具体语音的证据已经有了。在本句中specific speech sounds are recognized by babies as young as 6 months old是前面evidence的同位语, 因此应由that引导,答案应为C。