Choose the correct word from the given options to complete the senten…

The correct answer is Option (2) → Although

Conjunction of contrast (concession):

• Although (like "though" and "even though") is a subordinating conjunction: it joins a dependent clause to the main clause.
• It shows that the main action happens in spite of what the dependent clause says.
• This sentence: being tired would normally make a person stop, yet she kept working; the first clause is a concession, so "Although she was tired" is needed.
• Complete sentence: Although she was tired, she continued to work late into the night.
  Example: Although it was raining, the match went on.

Why the Other Options are Incorrect?

Option 1: However — Incorrect.

• However is a conjunctive adverb, not a conjunction; it cannot join two clauses into one sentence with only a comma. The idea needs two sentences: "She was tired. However, she continued to work."
• Placed before "she was tired", it would mean "in whatever way", which makes no sense.
  Example: The road was narrow; however, the driver went on carefully.

Option 3: Unless — Incorrect. Unless means "if not" and states a condition; "Unless she was tired, she continued to work" makes no sense.
Example: You will miss the bus unless you hurry.

Option 4: While — Incorrect. While mainly shows time (during the time that) or a contrast between two facts (whereas). It is sometimes used for concession in formal English, but "While she was tired" is first read as time; although states the concession plainly.
Example: She hummed a song while she cooked.

Contrast: although joins a clause of concession to the main clause; however links two separate sentences.