单选题 The development of the light bulb ______ partly as a result of the widespread availability of electricity and the need for cheap, clean light.
A. occurring B. was occurring C. was occurred D. occurred

【正确答案】 D
【答案解析】考的是语态和时态。讲的是过去的事情，用一般过去时。Development的出现或发生，可用主动态。选项D是正确的。