OG13 SC 第72题~求解！！！多谢各位！

We use the past perfect (or the "double past") when we have two discrete events in the past; the older of the two events takes the past perfect.


In this particular sentence, we have to be very careful. "led" is a discrete event in the past, so an earlier related event would take the past perfect. However, "existed" isn't related to "led";


it's actually related to the "are now" at the end of the sentence. Since "are now" is the present, we use the simple past "existed" to show the relationship between those two actions.


quote：


more knowledge on past perfect：


note that the past perfect can be used, roughly speaking, in two different circumstances:


1) for past actions that were ongoing until, or relevant to, a later past action (this is what you're thinking about);
OR


2) for past actions that were ongoing until, or relevant to, a later past TIME MARKER.


for #2, the second time marker could be something explicitly mentioned in the sentence.


before the introduction of soft landing mats, high jumpers had been forced to use the western-roll style of jumping


--> note that there is no second verb, but "the introduction of soft landing mats" is a time marker.


however, if the context of the sentence clearly IMPLIES a second time marker, then that second time marker may not even have to be mentioned explicitly.

We use the past perfect (or the "double past") when we have two discrete events in the past; the older of the two events takes the past perfect.


In this particular sentence, we have to be very careful. "led" is a discrete event in the past, so an earlier related event would take the past perfect. However, "existed" isn't related to "led";


it's actually related to the "are now" at the end of the sentence. Since "are now" is the present, we use the simple past "existed" to show the relationship between those two actions.


quote：


more knowledge on past perfect：


note that the past perfect can be used, roughly speaking, in two different circumstances:


1) for past actions that were ongoing until, or relevant to, a later past action (this is what you're thinking about);
OR


2) for past actions that were ongoing until, or relevant to, a later past TIME MARKER.


for #2, the second time marker could be something explicitly mentioned in the sentence.


before the introduction of soft landing mats, high jumpers had been forced to use the western-roll style of jumping


--> note that there is no second verb, but "the introduction of soft landing mats" is a time marker.


however, if the context of the sentence clearly IMPLIES a second time marker, then that second time marker may not even have to be mentioned explicitly.

now的问题不是关键

还是那句老话，你得知道过去完成时和一般过去时是在同一条时间轴上面的，他们两者是在一条线上的两个不同点


这里led和existed是没有关系的，恐龙存在和谁激发了科学家的发现是没有必然的联系的，是两条时间线，而不是一条线上的两个点


至于current的问题
假设是current就会有歧义


current （temperate areas）还是current and temperate areas？


currently的话就只能当做副词去修饰temperate


没有歧义