Write the next sentence in this paragraph:

How to exercise a mother dog
Take the dog on walks.
You should take your dog on daily walks. If you walked your dog regularly before pregnancy, you may continue with this schedule.

Select from:
[a]. If your dog periods more often, you should increase your walks to twice a day. In the first few weeks, you can exercise your dog at least once a day (45 minute walks).;
[b]. If not, start taking the dog on fifteen minute walks once or twice a day. After the first month of pregnancy, you may need to shorten the length of these walks to prevent overexerting your dog.;
[c]. You should begin with a walking regimen of two regular walks every two weeks, every two to three days. Increase the frequency each day until your dog gets the most exercise.;
[d]. The mother's womb reserves fertile water and provides the pregnant dog with this fertile water. You can take the mother dog on walks from 1:00-12:00 every week.;
[b].