Mrs. Hanson, a housewife bent on getting ________ higher education, has been going to college, a few courses at ________ time, for 7 years.

A．a; a

B．不填; the

C．the；a

D．不填；不填

有关上颌第一双尖牙根管的描述正确的是（）

A.多为近远中径窄，颊舌径宽的单根管，少数为两根管

B.多数情况下为颊舌侧两根管，仅少数为单根管

C.舌侧根管较颊侧根管细小

D.多为颊侧两根管，舌侧单根管，且很细小

E.以上都不是