2. The author implies that there were fewer cases of breast cancer in the past ______.
A
[解析] 推理题。题目问的是过去的乳腺癌病发率较低的原因是什么。定位到第二段“Although some of the increase can be attributed to changes in reproductive patterns, ..., much of the rise is due to the increased detection of smaller, earlier-stage cancers with the widespread adoption of mammography screening in asymptomatic women”意为“尽管乳腺癌发病率的提高一部分可以归咎于繁殖方式的变化,……,但是主要还是因为随着乳腺扫描仪的发明许多无症状病例和早期病例被发现造成的”,可知过去乳腺癌发病率较低的原因之一可能是由于没有发明出乳腺扫描仪,故许多无症状病例未被发现。故选A。