Explanation:
The sentence compares the past ("used to walk") with what happens nowadays (present habit).
So the second part needs a verb that shows a present, repeated action.

Now the options:
- A. was going — past continuous, wrong (talks about past).
- B. is going — present continuous, suggests happening *right now*, not habit.
- C. seldomly goes — wrong word ("seldomly" is not standard English; we say "seldom").
- D. goes — simple present tense (correct for habits).
- E. has gone — present perfect, not right for a regular habit.

Therefore, the correct answer is D. goes.

Full sentence:
In the past his father used to walk, but nowadays he *goes* to work by bicycle.

(NOTE: "by bicycles" should ideally be "by bicycle" — singular — but that's a minor thing depending on how strict your exam is.)

Want another quick example on how simple present tense fits habits?