p. 107, ex. 3
a) 1. How are you getting on? 2. Where are you going to? 3. I have been training here only for a short while. 4. He has been attending this sports club for two years,
b) discuss length of time — 1, 2
expresses the length of time of an activity which began in the past and is in the progress right now — 3, 4.