Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 21 to 25.

One problem that all the countries in the world have in common is litter. In an effort to get the situation under control in the UK, the government organises a national spring cleaning day, (21) ________ takes place every year on the first day of spring. The aim is to convey the message that local areas will be better places to work and live if people look after them. Ministers believe that chewing gum companies and fast food outlets are partly responsible for the problem and (22) ________ they are hoping to persuade them (23) ________ on the day. Studies carried out by the organisation Keep Britain Tidy have shown that more than half the population is guilty of dropping litter, leaving it to city councils to (24) ________ the mess. This means diverting cash from fundamental areas, such as care of the elderly, to foot the bill. It has been calculated that more than £800 million every year is spent (25) ________ cleaning city streets. The government hopes to change people's behaviour by making dropping litter just as unacceptable as illegal parking.