1．The invention of the typewriter was a great ________ communication and printing.
A．contribution for B．contribution to C．contributions for D．contributions to
解析：因空格前有不定冠词a，决定contribution用单数；contribution后用介词to，而不用for。
答案：B
2．Jack often looks after her son ________.
A．in absence B．in her absence C．in her absent D．at the absence
解析：句意：“在她不在时Jack经常照看她儿子。”in the absence of /in one’s absence习语“在……不在时；在……缺乏……”，故答案是B。
答案：B
