Backshift in the reporting clause is optional when the time reference of what's being reported is still valid at the time of the report.
They thought that the prison conditions have improved.
I heard her say that she is studying business administration.
are both correct, as well as:
They thought that the prison conditions had ...
I believe that in your examples there is no difference. Because people will interpret it correctly. But strictly speaking when you add can it could point to someone having an ability to do a certain thing, and adding the word can would thus change the meaning of the sentence..
I can see colours
I see colours
The first one would ...
You cannot show up.
This means you won’t be able to show up, or that you shouldn’t show up.
You can not show up.
This means you can choose to be a no-show, and is what the article is saying.
You can learn to dance.
You can dance to music.
You can march to the beat of a different drummer.
These are all grammatically correct, and the “to” is ...
Either are perfectly acceptable - in terms of wasn't able vs couldn't. I have heard both said in the past and wouldn't think either sounded unnatural.
On a side note, unless you have the exam in your hand and pointing at a particular question, I would change it to:
I wasn't able to/couldn't do that question
For example, you're chatting after an exam:
They both make perfect sense, and each is normal and acceptable.
The one consideration I can think of that would distinguish the two is simply the fact that I couldn't is only two words as opposed to the four in I wasn't able to.
Also, I couldn't is easier to pronounce than I wasn't, given the movement of the tongue required for each.
As such, the I ...
You are correct that the old lady is speaking about a routine or habit, but she is referring to a routine that she used to have (i.e. in the past), which was in response to actions that you used to do.
In the sentence, "I used to stay up every night when you would go out with your friends", you used to go out with your friends and, when you did, she would ...
You can use could without a verb following like all modal verbs, but the context should make sense. Could should only be used if the sentence is expressing ability to do something and is conditional.
Could infers that one can do it now and after, but you used the past-tense of to be (was).
Here's an example which would work.
Person 1: He could make the ...
The usual form would be will occur, because the program will do the same thing for the same input. As this is habitual, it's also common to see present tense: occurs.
Which modal verb you choose depends on what you want to emphasise:
Use can to emphasise that the program is capable of detecting some error. "The program can generate an error if the input ...
As you mentioned, after modal verbs (can, could, would should, ...) we are not allowed to use to. Instead, we need to use the simple tense of the verb. So, here using to after can is incorrect and "Can not show up" is correct.
WOULD | Grammar | EnglishClub:
Would is an auxiliary verb - a modal auxiliary verb.
"I would like to eat rice."
"I" is the subject.
"would like" is the verb phrase
"like" is the verb, and "would" is the auxiliary verb.
See grammar terms:
Expresses an action (break, call, tremble, skate), an occurrence
(happen, occur) or a state of being (...
It's a kind of variation on the third-conditional / hypothetical. It describes a past situation that didn't happen, and the potential consequence if it had happened. Here's how it could be phrased as a standard example of the third conditional:
If her father had sold the bows, it would have given the government the idea that her father was arming the ...
In this context, "possibly" actually lends doubt to the statement, and will often be seen with emphasis of some kind, when written.
So, your first example means that there is lets say 0 to 10% chance, while the second means anything from 1% to 100%
The context and the tone of voice used will make it clearer exactly how much difference there is.
I told him the store will be open tomorrow.
It's 100% possible for both of these to be true at once and there is no contradiction.
You have completed telling him something.
The store will be open tomorrow.
An example would be if this order of events happened:
Store closed at 6pm.
You told your friend, at 6:30pm, that it will open tomorrow at 10am.
The answer can be given in the context of the British council's web page you referred to. Here is a longer quote:
We use will to express beliefs about the present or future:
John will be in his office. (present)
We'll be late. (future)
We will have to take the train. (future)
We use would as the past of will, to describe past beliefs ...