I've been taught that the Present perfect tense is used when an action happened in the past and it is important now (or when it happened in the past and it is still ongoing).
Though, look at these examples:
Carla can't play basketball. She has broken her leg.
Carla can't play basketball. She broke her leg yesterday
The first example is the same as the second one, but the 2nd example is just using simple past tense. So, why grammar says that we have to use Present perfect tense when the action has an influence in the present since I can use simple past tense and it would have the same influence in the present! (Like, the first example and the second one have the same influence in the present, because Carla can't play basketball today in these 2 examples)
I've been searching for a while and always says that "it is something that influences the present". But, if I say "She broke her leg yesterday. That's why she can't play" it would have the same meaning. So, that's why I am "confusion".
Best Answer
This statement tells us when the person's leg got broken.
The emphasis is shifted to a specific point in the past; she is not breaking her leg now, ergo "She is breaking her leg yesterday" is grammatically unsound. Likewise we would not say "She was breaking her leg yesterday" because the action is not an ongoing one. However, it is possible that she might break it again some time in the future, ergo "She is going to break her leg" is an acceptable statement if the speaker was warning the interlocutor of an imminent event that was about to take place in the not distant future.
This statement tells us why she cannot play basketball today.
The listener is less interested in knowing when the accident happened, the focus is on the now and present. The sufferer may have broken their leg a day ago, or even two weeks ago, it doesn't matter when, what matters is the person is (still) unable to play. Although the accident is clearly established in the past and cannot be repeated, we are interested in the present consequences of that past event.
The present perfect can be used (it is not obligatory by any means) to answer these types of questions:
The simple past can be used to answer these types of questions