A-A+
Scientists have found that there are four leve
问题详情
Scientists have found that there are four levels of sleep, each ______ a little deeper than the one before.
A．is
B．was
C．being
D．to be
参考答案
正确答案：C
解析：该题考查考生对独立结构的掌握。being a little deeper then the one before在这里对前面的陈述提供进一步的信息。
