Which of the following skills would you expect to see in Krystyna, who is a 4-month-old infant?
a) She can make basic crawling movements and can move a few feet at a time.
b) She can roll over from her belly to her back or from her back to her belly.
c) She can follow movements with her eyes and hold an object placed in her hand.
d) When an object is within range, she can pick it up with her thumb and forefinger.