Join the following sentences to make one complete sentence without using and, but or so.
He was very ill. He did not take any medicine.
Topic: Synthesis — clause of contrast
Answer
Although he was very ill, he did not take any medicine. (Also acceptable: In spite of being very ill, he did not take any medicine.)
The relationship is CONTRAST — he was ill AND YET took nothing — so ALTHOUGH or THOUGH is correct.
The alternative uses a phrase rather than a clause: "In spite of being very ill" or "Despite being very ill". Note the forms: although / though + full clause (he was ill) in spite of / despite + noun or -ing form (being ill) Mixing them — "despite he was ill" — is wrong.
A common error to avoid: never use "although" and "but" in the same sentence. One or the other.
METHOD for every synthesis question: identify the relationship first — reason, contrast, time, condition — and the conjunction follows from it.