[单选题]
In a transformer, if the secondary coil contains mob6e/c6y2ih8r1,r jn.ocu (dhbm8 vgwre loops than the primary w gw.twx/nu 5s61tl 5bcoil thes/g 61unxwt5w5 l. twbn it is a
A. step-up transformer.
B. step-down transformer.
C. either a step-up or a step-down transformer.
D. can not be determined.
