to sit up straight; to straighten one's posture; to straighten up
to straighten oneself; to straighten one's clothes and one's posture; to adopt a more serious attitude
to go to the bottom of an affair; to inquire into the origin
to sit up straight; to straighten one's posture; to straighten up
to go to the bottom of an affair; to inquire into the origin
to inquire (about); to enquire; to ask; to interrogate; to question intensely; to grill (someone about something)
to find out the truth; to ascertain; to clarify; to confirm; to verify