definite article

Generally speaking, the definite article implies a closed set, whereas the indefinite article can be regarded as an open set.

For example: “This is the watch that I bought yesterday.” implies that you only bought one watch yesterday, or that the current discussion is about a single watch.

If you said, "This is a watch that I bought yesterday," it implies that it's not the only watch you bought yesterday or at least, that a single watch is not the subject of the discussion.

With the, the noun phrase in context fully specifies who is contacted to the level of practicality. Without the, the noun phrase is less specific and may apply to some who are not contacted:

Peugeot said it will soon be contacting customers concerned by its recall.
Customers contacted are (or have been) concerned by the recall.
Peugeot will contact some but perhaps not all of its customers concerned by the recall.

Peugeot said it will soon be contacting the customers concerned by its recall.
All customers concerned by the recall will be contacted.
Peugeot will contact the whole group of "customers concerned by its recall".

We are contacting concerned parties.
Parties being contacted are concerned parties.

We are contacting the concerned parties.
All concerned parties are being contacted.

Thank you for sending us fresh vegetables.
Thank you for sending us some fresh vegetables.
Thank you for sending us the fresh vegetables.

Thank you for sending us wine.
Thank you for sending us newspapers.
Thank you for sending us vegetables.

Thank you for sending us a bottle of wine.
Thank you for sending us a newspaper.
Thank you for sending us a carrot. We're ever so pleased.

SOME NOTES

When we say we are putting a dent in something, we mean that we are making a small but noticeable change.

Muscle relaxant is the phrase that is commonly used. Obviously, muscle relaxants tend to keep one very relaxed, but sometimes the effect is almost like a narcotic, too. She seems to be suggesting that she wants to meet with her ex-husband while she will feel no pain and while she won't get angry, upset, or otherwise worked up.

STILL

Adverbs are slippery little beggars. They can appear in different places in a sentence and often there is little or no change of meaning.

I still can (see the moon), or whatever.
Consumers still must save more.
I have still to do my homework.
I still have to do my homework.
No significant difference.

Still, I have to do my homework.
This time, still is a sentence adverb, meaning something like nevertheless.

Gerund and possessive

1. I hate the boy skating on the sidewalk.
2. I hate the boy's skaiting on the sidewalk.

The first sentence indicates that I hate a boy. The specific boy who I hate is the one who is skating.

The second sentence indicates that I dislike skating. The skating which I dislike is being done by the boy. I may like the boy very much--it's the skating to which I object.

This one can go either way depending on the shade of meaning that you intend:
I watch Emily's dancing because I want to learn from her. (If you mean that it is the dancing that you are specifically watching, not Emily.)
I watch Emily dancing because I want to learn from her. (If you mean that it is Emily that you watch, and you usually do it while she is dancing.)

Example;

During her stay at school, (name) maintained excellent academic achievement.

Yes, it would be wrong to use "staying" in this sentence.
Your stay ... = the period of time when you were there.
Your staying ... = your continued attendance at the school.

"During her time as a student at [NAME of SCHOOL], [NAME] maintained an excellent academic record."

"While a student at (name of school), X (name of person) .....maintained excellent academic achievement" .