3T场强的磁共振系统一般为（）
A.超导型
B.永磁型
C.常导型
D.混合型
E.U形磁铁型
参考答案：A
– We can invite our teachers to the farewell party next Saturday.
-- Yes, ______? I’ll call them at once.
A．what for
B．what
C．why not
D．why
（）twice, the postman refused to deliver our letters unless we chained our dog.
A. Being bitten
B. Bitten
C. Having bitten
D. To be bitten
