I don't often exercise.(改同义句)I ____ ____ ____exercise.我总是感觉多了一个空,但是老师说没有.

I don't often exercise.(改同义句)I ____ ____ ____exercise.
我总是感觉多了一个空,但是老师说没有.

用hardly ever do 因为exercise可以作名词也可以作动词.
I don't often exercise.中它做动词,而I hardly ever do exercise.中 exercise做名词放在do后.