Difficulty: Easy
Correct Answer: in crushing
Explanation:
Given sentence
'… the Protestant leaders joined the princes at crushing them.'
Concept/Approach
The verb 'join' takes the preposition 'in' when followed by a gerund to denote participation in an activity: 'join (someone) in doing (something)'.
Correction
'joined the princes in crushing them.'
Common pitfalls
'at crushing' is unidiomatic; 'into crushing' changes meaning; 'without crushing' negates the action.
Final Answer
in crushing
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