问题
选择题
________ have an internal clock that controls the beating of our heart, and the ________ of our breathing.
A．Human being; steps
B．Humans; pace
C．Human beings; steps
D．Man; pace
答案
答案：B
B 考察名词。句义：人类体内有一个生物钟，它控制我们的心跳和呼吸的节奏。因为谓语是have，所以排除AD，humans="human" beings，但steo的含义是脚步，步伐；