单选题 Mary could invite her friends to the house at her own ______ if she told her mother in time.

【正确答案】 B
【答案解析】(discretion斟酌决定的自由，处理权限)。句意为：如果玛丽及时告诉母亲，她可以自行邀请朋友到那个房子里去。A．prudence慎重；C．reaction反应；D． exertion尽力。