Which statement is an opinion? a. many presidents have admired abraham lincoln. b. abraham lincoln was the sixteenth president of the united states. c. abraham lincoln was the best president the united states ever had. d. abraham lincoln often wore a top hat.

C. because it says "best" and that is an opinion. Like some people might not have liked him so it was an opinion, not a fact. 

The last one i think

Dogs have been considered man’s best friend for decades! most likely because of their kind and loyal nature. they make splendid companions. their loyalty is beyond compare and after all, a dog is the only thing on earth that loves you more than he loves himself! dogs see us as their friends and leaders, they’ll do anything in their power to ensure your comfort and safety.