①我国人口基数大
②我国人口素质偏低
③我国男女性别比失衡
④我国人口老龄化速度加快
A:①②③
B:①②④
C:①③④
D:②③④
——Have you watched the TV report about MERS? ——Yes, it's _________ new dangerous disease(疾病).