GWD一数学题目，请教各位兄弟姐妹。谢谢勒。。

A total of 30 percent of the geese included in a certain migration study were male. If some of the geese migrated during the study and 20 percent of the migrating geese were male, what was the ratio of the migration rate for the male geese to the migration rate for the female geese?
[Migration rate for geese of a certain sex = (number of geese of that sex migrating) / (total number of geese of that sex)]
A. 1/4
B. 7/12
C. 2/3
D. 7/8
E. 8/7

（注：看勒几遍没有看懂，理解50%的基础上算出来是A。可答案是B）希望知道的兄弟姐妹指点一下。非常感谢。）

再加一道可以么？我觉得很奇怪的一道题，找不出什么关联：

K is a set of integers such that if the integer r is in K, then r + 1 is also in K，Is 100 in K？
(1) 50 is in K.
(2) 150 is in K.

哦，忘记说勒，答案是A。。。顶该呢？？