A Step Up transformer :

• A. Steps up the level of Voltage
• B. Steps down the level of current
• C. Step up the level of Frequency
• D. (a) and (b) only

Answer: (D)

Step up transformer increases voltage level (decreases secondary current).
Step down transformer decreases voltage level (increases secondary current).

In normal operation of transformer power, flux and frequency remain same (or almost same) at input and output.