这几道题是总结出的考试中错题,还是不太明白,麻烦您帮助具体解释一下选择的理由,

这几道题是总结出的考试中错题,还是不太明白,麻烦您帮助具体解释一下选择的理由,
About____students in our college are from other countries in Asia
A  three  hundred       B    hundred     C  hundred s of      D  hundreds
The table   is made _____ wood and the paper is also made ______
A  of  of      B from    from  C  of   from      D from    of
Helen students Maths ________then before ,Now she makes fewer mistakes thanJane
      A careful       B  more  careful       C         carefully D more  carefully
4.The cars move_______in a treffic jam,It is a big problem
     A  slightly    B quickly       C fiercely      D slowly
5.We will stay in an air-conditioned   room if it _______too hot
     A  will    be     B was    Cis      D be
6.______useful in formation it is
     A  How     B How a         C  what         D what  a
7.My father ___back from America in three days
  A  comes     B came    C will come     D has come