英语从句时态的问题

英语从句时态的问题
It took him four years to stage this elaborate joke simply to prove that critics do not always know what they are talking about.
此句出至新概念英语.
从句.do not always know what they are talking about.
的时态(do not.are talking...)没有与主句的时态一致?
理由越充分者加分.
选2楼而不选一楼,原因有2点
1.一楼的例句时态错了.
The teacher told us that the earth circle(s) around the sum.
2.一楼的翻译不对,do not always不是译成"总是不知道"
而是"不是总能知道",,,,概念不同,前者是全完否定,后者是不完全否定.
二楼说的有一点对,考试不考模糊的东西,
只考容易被突略的东西.