Question on particles は and を


In a language exercise, I was supposed to write the following in Japanese:
"Please close the window." Intuitively, I thought, since 窓 is the direct
object of 閉めて, then probably

窓を閉めてください

I found out the correct answer is:

窓は閉めてください。

My question is, is 窓を閉めてください a grammatical sentence at all? If it is, then
does it mean something different from 窓は閉めてください?

Further on in the same exercise, I came across another sentence:

その窓を閉めてください

I thought, strange, why is it now を and not は? So now my other question is: is
その窓は閉めてください grammatical? And if it is, does it mean something different from
その窓を閉めてください?

May I add that it's an online exercise, so I had no teacher to ask. Thanks for
helping.




窓を閉めてください is perfectly correct and natural as the translation of "Please close
the window." If there is no other context, there is nothing wrong with your
translation.

窓は閉めてください is also a perfectly grammatical sentence, but its meaning is
different, because 窓 is now _topicalized_ using は. Note that は is a _topic_
particle, and it can replace both が and を. In other words, 窓 is still the
direct object of 閉める, but を is "masked" by the topic marker は. Since 窓 is
topicalized, this sentence is now about the window itself; the speaker wants
to state a fact, a rule or something regarding this window. A very literal
translation is "As for the window, please close [it]". A sentence like this
implies you have to always close this window (e.g., at the end of a day), and
you have to remember this as a rule.

To summarize, if the original English sentence is a simple one-time request,
窓を閉めてください is correct. If the original English sentence is presented as a rule
to remember, 窓は閉めてください is also correct.




窓を閉めてください is perfectly correct and natural as the translation of "Please close
the window." If there is no other context, there is nothing wrong with your
translation.

窓は閉めてください is also a perfectly grammatical sentence, but its meaning is
different, because 窓 is now _topicalized_ using は. Note that は is a _topic_
particle, and it can replace both が and を. In other words, 窓 is still the
direct object of 閉める, but を is "masked" by the topic marker は. Since 窓 is
topicalized, this sentence is now about the window itself; the speaker wants
to state a fact, a rule or something regarding this window. A very literal
translation is "As for the window, please close [it]". A sentence like this
implies you have to always close this window (e.g., at the end of a day), and
you have to remember this as a rule.

To summarize, if the original English sentence is a simple one-time request,
窓を閉めてください is correct. If the original English sentence is presented as a rule
to remember, 窓は閉めてください is also correct.

