Réponse :
Bonjour,
Thanks for your email. Sorry to hear you've been so ill. Mike said you _WEREN'T ABLE_TO_____ get out of bed this morning. It's a shame you _COULDN'T_ make it to Prof Andrew's lecture today, as it was really interesting. It was all about cell mutation. Don't worry though. You CAN_ find his notes posted on the course blog. He's aslo uploaded some great images that he showed us in the lecture. Our next project is to research an aspect of cell mutation, but we WON'T BE ABLE TO access the instructions for that until tomorrow.
Also Sara says she's tried several times but COULDN'T reach you on your mobile.
Have you had it switched off? Give her a call if you CAN.
Explications :
CAN / COULD/ BE ABLE TO sont des modaux qui expriment la capacité.
COULD : conditionnel passé. Exprime la possibilité ou la capacité.
( on peut dire que c'est CAN au passé car CAN ne s'utilise pas au prétérit, on le remplace par COULD )
( c'est le contexte, la situation d'énonciation, qui te permet de savoir si c'est passé ou conditionnel )
CAN ne se met pas au prétérit ni au futur, il faut utiliser son équivalent TO BE ABLE TO
EX : présent : I can go to school
prétérit : I was able to go to school
futur : I will be able to go to school