第一节 单项填空（共15小题；每小题1分，满分15分） 21.although it had been________ struggle for him to finish______ experiment, he enjoyed the result with________ satisfaction. a the, an, / b a, the, / c a, an, a d /, the, a 22.upon ______the classroom， i started thinking about my mother. a. leave b. leaving c. left d. to leave 23.—i think your brother is managing your parents’ shop the wrong way. —i agree. i regret _______it myself! a. to run b. not to run c. not running d. running 24.the lucky dog missed _______by his teacher, though he had made a big mistake.
