[单项选择]The attraction of opposite charges is one of the force that keep electrons in orbit around of nucleus of an atom.

Details of telephone charges can be found at the front of any telephone directory ( 电话簿), where you will see that the cost of your call will depend not only on the duration and distance but aim on what time of day the call is made and sometimes on whether or not it is made at the weekend or during the week. Between most places in Britain it is now possible to dial direct by STD ( Subscriber Trunk Dialing) (拥护直通长途电话). Charge rates are higher for calls made from coin - box phones and call offices than for those made from ordinary lines, and calls connected by the operator are normally more expensive than calls you dial direct.
STD facilities now exist between Britain and most countries in Western Europe and also with a number of other overseas countries beside. Other calls will require the assistance of the operator. Charge rates for international calls depend broadly on the same factors as for inland calls. Full details of international telephone charges and servic
A. direct from ordinary lines
B. through the operator
C. from call offices
D. from coin - box phones