在三相对称正弦交流电路中，Y型连接的中性点电位为（）。
A.线电压；
B.相电压；
C.100V；
D.0。
参考答案：D
A firm is choosing among three short-term investment securities: Security 1 - A 30 - day U. S. Treasury bill with a discount yield of 3.6%. Security 2 - A 30 - day banker’s acceptance selling at 99.65% of face value. Security 3 - A 30 - day time deposit with a bond equivalent yield of 3.65%. Based only on these securities’ yields, the firm would:（）
A. prefer the banker’s acceptance.
B. prefer the time deposit.
C. prefer the U. S. Treasury bill.
炼钢工应经常检查（）、烟罩、烟道和炉口等处是否有漏水现象，如有应立即停止吹炼。
