第30题: [单项选择]PRA的阳性值为() A. >10% B. >5% C. >15% D. >20% E. >30% 参考答案:A
第31题: [单项选择]Many rare species of plants and animals are threatened with______ with the worsening of environment and mass hunting. A. extinction B. migration C. destruction D. extraction 参考答案:A 答案解析:[解析] 逻辑关系题:因果。物种数量本已很少,再加上环境恶化和大规模的狩猎,它们面临的应该是物种灭绝的威胁。[A]extinction“灭绝”符合题意。[B]migration“移民”、[C]dest