1. C
2. C
3. D
These are the best choices.
The answer is B because it puts a coma in the correct spot to pause between the first half of the sentence and the second. The others either randomly placed a period, using the wrong word choices, or made it a run on sentence. :)
C is the choice I would make because I believe the writer is planning to answer this question: "and how come we think dogs are so smart". The writer never tells us what dogs can't do (a) or mention others being dumb (b) and doesn't make fun of humans (d)
