皮质醇增多症最常见的病因是
A．垂体ACTH分泌过多
B．原发性肾上腺皮质腺癌
C．医源性皮质醇增多症
D．异位ACTH综合征
参考答案：A
－I think students should be allowed ______ homework with friends.
－I disagree. They talk instead of ______ homework. [ ]
A. do, doing
B. to do, to do
C. to do, doing
D. doing, to do
现有三个自然数，它们的和是1001，这样的三个自然数的公因数中，最大的可以是______．
