The owners of Pixie, a normally playful puppy, didn't know why she had slowed down and would whine any time she was picked up. The answer came when a veterinarian removed the 7inch long, serrated steak knife the dog had somehow swallowed. "If I had known a knife was in her, I would have freaked," said owner Tony Strollo.

The English BulldogGerman Shepherd mix was not even 2 months old and weighed just over 10 pounds when she wolfed down the knife, probably on Jan. 14. The knife apparently fell on the floor during a meal and nobody noticed. No one, that is, except Pixie.

Teeth marks found later on the knife testify to the fact that the puppy gnawed at it before she swallowed it.

Dr. Jo Ann Helm, a veterinarian, who found and surgically removed the utensil Jan. 21, said the knifed lay neatly packaged down Pixie's throat, with the handle pushing down on the stomach.

The first sign that something was wrong came when the pup tried to cough something up, but nothing happened. Then Pixie started acting funny. She couldn't coordinate her front legs, and she would give a tiny yelp when people picked her up, the Strollos said.

A first trip to the vet revealed nothing. Xrays were taken on a return visit and clearly showed the knife.

"Dogs swallow anything...pantyhose, balls, sticks," Helm said. "Just like a young human child, a puppy explores with its mouth."

a) The conclusion argued for in this passage is that the cause of Pixie's problems was a 7inch long knife lodged in her throat. Charitably schematize the argument for this conclusion.

b) What is the implicit question which guides this argument?

c) State two rival conclusions which are compatible with the support claims.

d) Provide some new evidence which would significantly raise the plausibility of one of the rival conclusions you offered in (c).