(单选题)

Why researchers limit their study to the month of September? ( )

A.cause more ships can sail in Arctic waters in September.
B. Because the day lasts for more than 24 hours in September.

B.Because sea ice is at its highest point in September.

C.Because polar bears will be on land in September.

参考答案：A

参考解析：

根据原文中的第二自然段......This is when sea ice is at its lowest point and most ships pass through Arctic waters.可知此时海冰处于最低点，大多数船只通过北极水域。选项A：因为9月份更多的船只可以在北极水域航行；选项B：因为九月的一天要持续24个多小时；选项C：因为海冰在九月达到最高点；选项D：因为北极熊将在九月登陆。故本题正确答案选A。

知识点：细节题英语阅读理解通用英语