A、Do extra work if necessary. B、Change the spark plugs only. C、Clean the spark plugs only. D、Charge her more than ￡ 10 if necess

The engine of Margaret’s car was not running smoothly. The spark plugs needed cleaning. Margaret could have done the job herself, but garages have special equipment that does such things very thoroughly.
    Like her father, Margaret did not like being overcharged. She knew that garages do this sometimes. Sometimes they even charge for work they have never done. She told the repairman at the garage not to do any extra work, she wanted the spark plugs cleaned, and nothing more. Then she left, saying she would be back in a little while.
    When Margaret came back, the repairman handed her a bill for ￡ 10. Margaret knew this was more than it should cost to have the spark plugs cleaned. Then the repairman said he had put new ones in. Margaret decided she was not going  to stand for this, and began to get angry.
    "But the plugs were worn out; what else could I do?" the repairman protested. "How long should these new spark plugs last? More than a few months?" Margaret demanded. "Of come! Much longer than that!" The repairman said with great emphasis.
    "Well, then, put the old ones back in. I had new spark plugs put in only a few months ago, and 1 had the job done here!" Margaret said.