外显子一内含子连接区的序列高度保守，该序列与RNA剪接机制相关，是RNA接的信号序列。 ( )
参考答案：对
He was sitting there ________ his cigarette. Without any words, he seemed to be ________ deep
thought. [ ]
A. at; in
B. over; in
C. with; at
D. with; over
对称三相电源星形连接，线电流等于（）。
A.相电
B.相电流的1.732倍
C.额定容量除以额定电压
