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

How to teach a dog to smile
Pay attention to time.
Teaching a dog to smile is similar to teaching him any habit, so you'll need to know the basic tenets of dog training. Timing makes a huge difference when it comes to successfully training a dog.

pick from the following.
(A). As a result, it's important to make sure that you're not getting your dog's attention out of fear or anxiety. That's because smiling will do the majority of the work for a dog-even if he doesn't look like that.
(B). Therefore, it's important to observe how often your dog sees or hears you while they are learning good behavior. You should be able to tell by the fact that they are learning to smile that there is something regarding your conversation.
(C). A dog must be rewarded the instant he obeys a command. Many people reward their dogs with a small treat or positive verbal praise, such as " yes! " or " good job! " some people invest in a clicker, a small mechanical device that makes a clicking noise when a button is pushed.
(D). Generally, teaching your dog to smile is the hardest aspect to learn and in turn should be taught in a combination effort and behavior, which will prevent tiring the dog out. If your dog isn't following these instructions, sit down and practice smiling with him.
(C).