考查定语从句.故用in which case.
分成两个独立的句子就可用B.
可以改成：He may win the competition.
And he is likely to get into the national team in that case.
whose 表示所有格 与这里的题意也不符合他可能赢得这场比赛，如果这样的话，他就可能进入国家队。不是“...的”的意思吗？which作定语，不是可以是whose吗？He may win the competition. And he is likely to get into the national team in that case.
in that case 如果要改为定语从句要用which

whose 是定语从句中一个常用的关系代词，表\" …… 的\"之意；它可以指\"人的\"，也可以指\"物的\"；

whose + n . 可作主语，宾语，功能与 which , whom (who )相同。如：
Mr King , whose legs were badly hurt , was quickly taken to hospital .
The boss in whose department Mr King worked had heard about the accident .

http://wenku.baidu.com/link?url=trMZHIEC2lAhviPc1Wx3o3-o5NvDjD-naoJIu_86khJNsviBi4ffoED9UnkRcg9t95VuFGumzMRP4Xatpgg-3brWb9Z7U92TYrfkFcFUfbq

您可以在这里详细了解