Abigail is 4 years old. She ignores people when they are in the room, and if people speak to her, she does not make eye contact. She also will not initiate communication, but rather just repeats what someone has said. Finally, Abigail shows high sensitivity to any loud noise or strong smell. She may be showing signs of:

a. attention-deficit/hyperactivity disorder.
b. a learning disability.
c. autism spectrum disorder.
d. bipolar disorder.