they haven't decided on whether they should go to beijing 为什么+了should

they haven't decided on whether they should go to beijing 为什么+了should
they haven't decided on whether they should go to beijing 为什么+了should

they haven't decided on whether they should go to beijing 为什么+了should
should是情态动词“应该”,whether they should go to beijing他们是否应该去北京.

decide后的宾从用虚拟语气sb+should do，与suggest相似，例如：The doctor suggested that he (should) run everyday.

should是个单词，情态动词

这句话要表达的意思是，他们还没有决定他们是否应该去北京。should是情态动词，应该；应当的意思