I am at this college/university because it was the only one that I gained entry to.
This college/university accepted me, so I chose to come here.
No other college/university accepted me, so I was left with no other choice except this one.
All three of these answers are good for explaining to someone that you chose the college/university that you are at because it was the only one that you were accepted into.
When you 'gain entry' into a school/college/university it means that you have either had an application accepted or you passed the entrance examination.
A) This was the only school I was accepted to and thus I decided to go there.
B) The reason why I decided to go to school here is because it was the only one I was accepted to.
A) using "thus" will mean that your first clause ("This was the only school I was accepted to") is the reason for your second clause ([why] "I decided to go there").
B) By stating "The reason why I decided to go to school here" at the beginning of the sentence you are being more direct with what you are ultimately trying to say. The second clause of the sentence explains why.
A) "thus"は、一つ目の節（This was the only school I was accepted to）が二つ目の節（I decided to go there）の理由であることを表します。
B) 文の始めに"The reason why I decided to go to school here"（この学校に通うことを決めたのは）と言って、最終的に自分の伝えようとしていることをよりストレートに表しています。この文の二つ目の節は理由を説明しています。
I decided to come to this university because they were the only one that gave me an offer.
I am attending this university because they were the only ones that gave me a place to study here.
I decided to come to this university because they were the only one that gave me an offer.
Here a decision was made because there was no other option.
The word "they" is used because the university has more than one person in it.
I am attending this university because they were the only ones that gave me a place to study here.
In this sentence you may be confused by the word "ONES" because we are speaking about more than one university having the ability to give an offer.
I decided to come to this university because they were the only one that gave me an offer.
合格したのがこの大学だけだったので、ここに来ることにしました。
他に選択肢がなかったのでそうした、という意味です。
大学には2人以上の人がいるので"they"を使います。
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I am attending this university because they were the only ones that gave me a place to study here.
合格したのがこの大学だけだったので、ここに通っています。
この文では、"ONES"という言葉に戸惑うかもしれません。合格する可能性のある複数の大学について言っているので、"ONES"を使います。
It was the only school I was accepted into, so decided to go there
I decided to go there as no other schools accepted me
If you are allowed to do something then they say you are 'accepted' to do it
If you make a decision on what to do then you say you 'decided' to do that
'only' means just one (only one) you could also say 'no other'
It was the only university that would accept me, so my choice was somewhat limited!
Well it seems like a sad story but you can always make a joke about it as in the example sentence.
If you have a limited choice, it means that you have few options in a certain situation.
It was the only school where I was admitted, so I went.
It was the only school that accepted me, so I chose to go there.
When we talk about getting in to college we often talk about 'admission' or 'being admitted' so this is a standard word to use. 'Chose' means 'decided on'.
イギリス 
アメリカ合衆国 
