在压实式造型过程中，影响型砂紧实度高低的主要因素是（）
A.压头形状
B.压实比压
C.型砂性能
D.砂箱高低
参考答案：B
It was along the Mississippi River _____ Mark Twain spent much of his childhood. [ ]
A. how
B. which
C. that
D. where
IEEE802.11a，它采用的频带为（）。
A、5GHz
B、2.4GHz
C、54GHz
D、11GHz
