The tracks that dinosaurs left show that they walked with th

[MdAbuAsad]

The tracks that dinosaurs left show that they walked with their feet directly under their bodies, as do mammals and birds, not extended out to the side in the manner of modern reptiles.

^^
Hi experts,
Can you help me to digest the things here, please?
In this correct sentence, 'left' is the first form of verb 'leave', and 'show' (past form-showed, past participle-shown) is the present form, right? In this sentence, dinosaurs left tracks-->This is past indefinite tense. That means: dinosaurs left tracks once upon a time-there is no existence of that 'tracks' right now. If this is the case how 'The tracks show (present form of the verb)' right now?

[Whit Garner]

"Left" is the simple past tense and the past participle of the verb "to leave." In this sentence, it is used in the clause modifying "tracks" in the simple past test. So at some time in the past, the dinosaurs left tracks (and they may or may not still be around if this is all the sentence said). Similarly, "yesterday, Mike left the lights on in the car..." - are they still on now? Who knows!

To leave:

Present: leaves/leave (He leaves the lights on... / They leave...)
Simple Past: left (He/They left...)
Future: will leave (He/They will leave...)
Present Perfect: has/have left (He has left... / They have left...)
Past Perfect: had left (He/They had left...)

Progressives (using the present participle "leaving")
(present) is/are leaving
(past) was/were leaving
(future) will be leaving
(present perfect) has/have been leaving
(past perfect) had been leaving

However, the main verb in the sentence is "show" = present tense. The past tense / past participle is showed and has/had/have shown.
Present: shows/show (She shows other people how to be brave... / They show...)
Simple Past: showed (She/They showed...)
Future: will show (She/They will show...)
Present Perfect: has/have shown (She has shown... / They have shown...)
Past Perfect: had shown (She/They had left...)

Progressives (using the present participle "showing")
(present) is/are showing
(past) was/were showing
(future) will be showing
(present perfect) has/have been showing
(past perfect) had been showing

A similar sentence with the same verb tense structure is the following:
The package that arrived this morning is for you.

[MdAbuAsad]

Thanks for the detailed!
I'm sorry to say that I can't figure out the difference between the followings,
1. Yesterday, Mike left the lights on in the car.
2. Mike left the lights on in the car.

Can you explain, please?

[Whit Garner]

Thanks for the detailed!
I'm sorry to say that I can't figure out the difference between the followings,
1. Yesterday, Mike left the lights on in the car.
2. Mike left the lights on in the car.

Can you explain, please?

Hi MdAbuAsad - I'm not sure what difference you're trying to figure out. But in #1, you are told exactly when the lights were left on (yesterday). In #2, you just know that the lights were left on at some point before now, but you don't know specifically when.