Why present perfect tense\past tense is used in these sentences?

Question

I used this link to practice on present perfect tense, and I have some questions:

Colin has left / left for Brazil this morning.

The correct answer is "left"; however, I think both answers are right, and it depends on the context. If we were still in the morning, then present perfect should be used, otherwise, use past simple because the morning period is already finished.

Ellen always write / has always written with her left hand.

I think using present perfect here is wrong because this is a simple fact, and present simple should be used.

Answer 1

For the first sentence, I agree with you. However, because of the time marker "this morning", I suspect that many natives would slip and use the simple past even if the morning hasn't yet ended, perhaps because of the sense of 'finality' involved in an international departure. Compare:

"Colin has just left for Brazil this morning."

which is a natural way to talk about an extremely recent departure, and definitely requires the present perfect. "Just" emphasises immediacy and forces the present perfect.

For the second sentence, both tenses are correct, as long as you make "always write" "always writes" to correct its agreement. The sentence in the present perfect sounds completely natural and grammatical to me. Perhaps this question is checking your 'third person -s' ?

Answer 2

The present perfect tense is used to describe something that happened in the past, but the exact time it happened is not important. It has a relationship with the present.

The correct verb choice for your first example is left. This is due to the fact that the sentence includes the exact, explicit time of this morning. Both of the following sentences are correct:

"Colin has left for Brazil." Colin's present condition is "gone," and the time in which he left is unimportant/unsaid.

"Colin left for Brazil this morning." Colin performed the action of leaving in the past, specifically this morning.

For the second example, both options fit (if "writes" is substituted for "write"), but the resulting sentences have slightly different meanings.

"Ellen always writes with her left hand." The fact that Ellen writes with her left hand is unchanging.

"Ellen has always written with her left hand." Up until the present, Ellen wrote with her left hand, but this does not imply she will continue to do so.