生物素
参考答案：
生物素是体内多种羧化酶的辅酶，如丙酮酸羧化酶，参与二氧化碳的羧化过程。
在图9所示电路的“○”中填上适当的电表符号，填上后要求灯L1和L2均能正常发光。
The biggest whale is _______ blue whale, which grows to be about 29 meters long—the height of______ 9-story building.
A．the; the
B．a; a
C．a; the
D．the; a
