Apple_____ to intense pressure from Chinese state media about its customer service practices, apologising to consumers in its second-largest market.

After a few courses on painting，Helen said she would ________oil pointing in her spare time.

Many experts agree that once these treasures are _______ to the air, great harm will be done to them. So they think it better not to unearth the treasures. 

He is seldom, ______, absent from school.

While we are having an exam, it is not proper to _____ our notes or dictionaries.