Tense in since-clause

[Sitifan]

Coco has learned Chinese since she ___ to Taiwan.
(A) has come (B) came (C) comes (D) is come
The answer is choice B. Is choice A also acceptable in colloquial English?
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Thank you very much for your reply.

[Yankee]

Hi Sitifan

The past simple is best if you are referring to a definite point in past time. In your sentence, the use of the past simple (since she came) suggests that the starting point for Coco's learning was basically the same time that she came to Taiwan.

If you use the present perfect (since she has come), the time that Coco began learning Chinese is not definite. It only tells you that Coco began learning Chinese sometime between her arrival in Taiwan and now. For example, if Coco came to Taiwan 5 years ago, possibly she began learning Chinese 2 years ago. In other words, it's not clear when she began.
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Also note that the use of the present perfect simple in the beginning of the sentence ("Coco has learned Chinese...") tends to suggest that Coco is now finished learning Chinese. If she is still learning, it would be better to use the present perfect continuous ("Coco has been learning...").
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[Sitifan]

1. I have been teaching English for six months.

2. I have taught English for six months.

3. I taught English for six months.

#1 means "I started doing it six months ago and am still doing it."

#2 possibly means the same as # 1, or could mean that once in the past I taught English for a period of six months.

#3 means once in the past I taught English for a period of six months.

Am I right?
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Thank you very much for your reply.

[Alan]

Spot on. You might care to read my current newsletter on tenses: http://www.english-test.net/forum/ftopic27293.html Take your time

Alan
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English as a Second Language
You can read my ESL story Colour Idioms