Multi-choice problem: Continue writing the next sentence in this paragraph:

How to deal with clinginess in older dogs
Talk with your veterinarian.
If your dog begins to change their behaviour, then you should take them to the veterinarian. Do not assume that your dog's new clinginess is simply related to aging.

OPT:
a). The fact is, it is becoming more difficult and harder to deal with your dog's clinginess. Your veterinarian will be able to offer you advice, and will also be able to recommend the best course of treatment.
b). Instead, you should talk with your veterinarian to see if this behavioural change is a symptom of a larger medical problem. For example, your dog may be in pain and find comfort in your presence.
c). If your older dog has suddenly developed an unhealthy appearance, or is suddenly seems less athletic, check if a physical change has been made. For example, if a new breed of dog seems to have slowed down its activity, then the weight may be significant.
d). While some symptoms may be easier to spot right away, be ready to make an informed diagnosis. Know the most common behavioral challenges in older dogs.
b).