He studied hard in order to pass the exam. (Make it complex)

• The correct sentence is: He studied hard so that he could pass the exam.
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• Simple Sentence এ 'in order to' থাকলে Complex Sentence এ রূপান্তর করার নিয়ম: 
- In order to এর স্থলে In order that অথবা So that বসবে। 
- এরপর noun phrase + can/could বসবে। 
- Present tense এর ক্ষেত্রে may এবং Past tense এর ক্ষেত্রে might বসে। 

Simple: We earn money in order to live a happy life. 
Complex: We earn money so that we may live a happy life. 

Simple: He studied hard in order to pass the exam. 
Complex: He studied hard so that he could pass the exam. 

Source: A Passage to the English Language by S.M. Zakir Hussain.