阅读下列短文，从每小题所给的A、B、C、D四个选项中选出一个最佳选项．

    Henry Bond was about seven years old when his father died．His mother found it 1to support the large family．However，she tried her best to do so．Also，she 2Henry，the eldest son，to school．

    At one time，Henry needed a grammar book for his study．His family was so 3that his mother could not afford one．

    One morning，Henry found that a deep snow had fallen，and the 4wind was blowing．"Ah，"he said，"it is an ill wind that blows nobody good．"With these words，he ran to the house of a neighbor，and offered his 5to move away the snow around it．The offer was accepted．When he finished the work，he received his 6．Then he went to another place for the

7purpose，and then to anther，8he had earned （挣得） enough to buy a grammar book．

    From that time，Henry was 9the first in all his classes．He knew no such word as"10"，and he succeeded in all he tried to do．Having the will，he always found the way．

下列运算中，错误的是（　　）