Kenisha Had an Ultrasound and Sees That Her Developing Fetus

Kenisha had an ultrasound and sees that her developing fetus is sucking its thumb. What can we infer from this?

A) That Kenisha is at least at the end of the first trimester
B) That the developing fetus must be at least 24 weeks of gestation
C) That the fetus will also have periods of wakefulness and sleep
D) That Kenisha has successfully avoided being exposed to teratogens during the pregnancy