In 1914 a total of 469,000 cars and trucks were produced in the United States, but in 1929 almost twice the numbers of tucks alone came off the assembly lines.
- the numbers of tucks alone
- that number of trucks alone
- the number of trucks by themselves
- as many trucks themselves
- as many trucks by themselves
答案选B 请问 C有什么不好的 twice在这里是什么词性？