those days 前面能加介词in 语法上说this,that,these,those构成时间状语时一般不加介词?如：Lily went to Beijing this morning.Father is writing novel these days.但：Tom lived a hard life in those days.这句话不是也正确吗?

those days 前面能加介词in 语法上说this,that,these,those构成时间状语时一般不加介词?如：Lily went to Beijing this morning.Father is writing novel these days.但：Tom lived a hard life in those days.这句话不是也正确吗?
those days 前面能加介词in
语法上说this,that,these,those构成时间状语时一般不加介词?
如：Lily went to Beijing this morning.
Father is writing novel these days.
但：Tom lived a hard life in those days.这句话不是也正确吗?
这是为何?请说明何时加介词,何时不加?有奖!

those days 前面能加介词in 语法上说this,that,these,those构成时间状语时一般不加介词?如：Lily went to Beijing this morning.Father is writing novel these days.但：Tom lived a hard life in those days.这句话不是也正确吗?
Tom lived a hard life in those days.中强调“在”那段日子的过程当中,因为“live”是个可延续性动词,所以用in
相反 Lily went to Beijing this morning.中went是不可延续性动词,this morning强调的仅仅是这个时间,没有时间短（延续性）的意义.所以不用in
Father is writing novel these days.句中,如果用进in也是可以的.
总的说来,强调时间点,动词是非延续性的,那么就不用
强调时间段,动词是延续性的,则可用可不用.
（我是英语老师,

如果强调的是一个时刻，那么不加，如例1
如果强调的是一段时间，那么加，如例2