Which of These Statements Is FALSE

Which of these statements is FALSE?

A) The radiographer must remain in the room during the exposure to be sure the patient does not move.
B) A lead/lead-equivalent apron and thyroid collar can be used to protect the patient from stray radiation.
C) Scientists know that exposure to large doses of radiation is more likely to cause biological harm.
D) The risk of harmful effects from dental x-ray exams is extremely small.