[单选题]
In a transformer, if 3c/buqe* su+x2 jfea8xc3nhg ,i3iw, the primary coil contains more loops than the secondary coil then it is acwf3, ge3jia2hn x i,8
A. step-up transformer.
B. step-down transformer.
C. either a step-up or a step-down transformer.
D. can not be determined.
