Seven-Year-Old Angelo Is Going to the Eye Doctor for the First

Seven-year-old Angelo is going to the eye doctor for the first time. One of the tests performed by the eye doctor is one that checks for pressure in the eye. To take this test, Angelo sits in a chair, places his forehead against an apparatus, and waits for instructions from the doctor. Then his eye is hit with a puff of air! While it doesn't hurt, it sure is startling and reflexively causes Angelo to blink. When the doctor says it's time to check the other eye, Angelo begins to blink as soon as he rests his head against the apparatus. What is the unconditioned stimulus in this acquisition scenario?

A) Angelo himself
B) Angelo's blinking
C) the puff of air in Angelo's eye
D) the feeling of the apparatus against Angelo's forehead