A、telephone them. B、buy them a gift. C、nothing, just go over. D、send them an invitation. A此题考查听细节的能力。抓住关键词before visiting，在听的时候

British people place considerable value on punctuality. If you agree to meet friends at three o’clock, you can bet that they’ll be there just after three. Since Britons are so time conscious, the pace of life may seem very rushed. In Britain, people make great effort to arrive on time. It is often considered impolite to arrive even a few minutes late. If you are unable to keep an appointment, it is expected that you call the person you are meeting.
    If you are invited to someone’s house for dinner at half past seven, it is considered good manners to arrive ten to fifteen minutes "late". An invitation might state "7 : 30 to 8: 00", in which case you should arrive no later than 7: 50. However, if an invitation says "sharp", you must arrive in plenty of time.
    "Drop in anytime" and "come see me soon" are idioms often used in social settings but seldom meant to be taken literally. It is wise to telephone before visiting someone at home. Although it is not necessarily expected that you give a gift to your host, it is considered polite to do so, especially if you have been invited for a meal. Flowers, chocolate, or a small gift are all appropriate. A thank-you note or telephone call after the visit is also considered polite and is an appropriate means to express your appreciation for the invitation.