Which of the Following Is the Result of Natural Development

Which of the following is the result of natural development?

A) The second time she gets her eyes tested, Sammy blinks when the buzzer rings because she predicts a puff of air is coming after the buzzer.
B) A baby begins to reach and fuss when his mother opens the refrigerator to get the bottle out.
C) A baby can sit up at six months but rarely can at two months.
D) Your cat runs to the kitchen at the sound of a can opener.