与电网并联的同步发电机；其（）子绕组通常采用（）接法。
A.转；Y
B.转；Δ
C.定；Y
D.定；Δ
参考答案：A
I am very worried because my son ________ most of his spare time ________ playing games on the computer.
A．concentrates；on
B．concentrates；in
C．focuses；to
D．focuses；in
喽面地价比土地单价更能说明土地价格水平高低。( )
