As you probably figured out you are being asked how many feet per hPa at different levels. In EASA-land we tend to remember the values for SL, the 500 hPa level and the 200 hPa level which are:
SL 27 ft/hPa
500 hPa (18 000 ft) 50 ft/hPa
200 hPa (39 000 ft) 100 ft/hPa
B looks best to me