Sunshine, I suspect one of two things...
You are unwell (eg, the flu... it is hard to get heart rate up when you are sick).
The second thing I strongly suspect is that you are fitter than you were a year ago, and your heart can handle exercise much more efficiently. Therefore, you can do the same ride, at the same effort/speed... but your heart is much more relaxed about it and ready for you to "step up".
Def choose "A". (And talk with your coach if you are concerned.)