In order to _______ a good knowledge of English, he gave up his job and went to study in an English school.
A:require
B:inquire
C:acquire
D:address
20世纪20~30年代的经济危机吞噬着整个世界。下列事件与这场危机直接有关的是( )
如图所示,用导线把电池、小灯泡和一段粗细均匀的电阻丝连接起来.当金属夹从电阻丝的某点,沿电阻丝向右移动的过程中,小灯泡亮度逐渐变暗.这表明导体电阻的大小跟导体的____ 有关.