i just don't understand___that prevents so many Amerians from bei_英语解答

i just don't understand___that prevents so many Amerians from being as happy as one might expect.
为什么是What it is

人气：155 ℃　时间：2020-01-26 03:05:21

解答

这是强调句型特殊疑问句用在了宾语从句中,用陈述语序.
It Is+被强调部分+that+其他
when is it that …….