English as a Second Language/Sequence of tenses


Dear Shannon,

Please note the following sentences:

"Galen studied how blood moves round the body." (studied: past; moves: present. Here, I checked a grammar book which says that we can use a present tense to express a fact. But what if I say "moved" instead of "moves, will it stop expressing a fact?

He said, "If I make a mistake, there could be an explosion." (make: present; could: past). Why "could" and not "can"?

Best regards,
Antoine Ghannoum

1. I think that would be ok, but typically the idea is that blood still moves around people's bodies, so it is something that happens in the present, too.  Now if the fact happened in the past (The forensic specialist examined how the victim was shot), you would use the past tense in all cases.

2. It expresses possibility, not ability.  http://www.onestopenglish.com/support/ask-the-experts/grammar-questions/grammar-

English as a Second Language

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Shannon Cole


I can answer questions related to learning the English and Spanish language.


I have taught ESL and Spanish since 1998 at the university and middle school levels. I am a native of the U.S., and have taught in both the U.S. and Mexico.

I am owner and operator of www.coleinstitute.com, an online language school.

Georgia TESOL in Action (1999)

B.A. in Spanish; M.Ed. in Language Education

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