Though … by opposition from his own supporters, the Chairman pressed ahead with his plans.

Analyze the question

The sentence is "Though ____ by opposition from his own supporters, the Chairman pressed ahead with his plans." The main clause already has its own verb, "pressed". The gap therefore needs a participial phrase, not a full verb with a subject.

Explain the concept

After conjunctions like though, although, when, while, if, you can drop the subject and the auxiliary verb be when the subject is the same as in the main clause. For example:

• "Though he was shaken by opposition..." becomes "Though shaken by opposition..."
• "While he was walking home..." becomes "While walking home..."

Here the Chairman is the one being shaken, so we need the past participle ("shaken"), which has a passive meaning: he was shaken by opposition.

Test each option

• A. shaking is the present participle, which is active. "Though shaking by opposition" is wrong because by signals a passive meaning.
• B. shook is the simple past. "Though shook by opposition" is ungrammatical.
• C. shaken is the past participle. "Though shaken by opposition from his own supporters, the Chairman pressed ahead..." is correct and means "Though he was shaken...".
• D. was shaken gives "Though was shaken by opposition...", which is wrong because there is no subject for "was". It would only work as "Though he was shaken...".

Answer: The correct option is C. shaken.

Tip: When you see a conjunction (though, when, while, once, if) followed directly by a gap and then by..., think "past participle". The phrase is a shortened passive, so test it by adding "he was" in front. If "Though he was shaken by..." makes sense, then "shaken" is the answer.