Some blood types are quite common, others are regionally , and still others are rare every

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(答案→)A. distributed
B. contributed
C. obtained
D. Convinced
解析：考查动词辨析。句意：一些血型很常见，而有一些呈地区分布，但仍有少量血型很罕见。distribute分布；分配；contribute；贡献；有助于；obtain得到；获得；convince使信服；确信。根据句意可知A项正确。故选A。